Here's a set of patches to add a general notification queue concept and to
add event sources such as:
(1) Keys/keyrings, such as linking and unlinking keys and changing their
attributes.
(2) General device events (single common queue) including:
- Block layer events, such as device errors
- USB subsystem events, such as device attach/remove, device reset,
device errors.
I have patches for adding superblock and mount topology watches also,
though those are not in this set as there are other dependencies.
LSM hooks are included:
(1) A set of hooks are provided that allow an LSM to rule on whether or
not a watch may be set. Each of these hooks takes a different
"watched object" parameter, so they're not really shareable. The LSM
should use current's credentials. [Wanted by SELinux & Smack]
(2) A hook is provided to allow an LSM to rule on whether or not a
particular message may be posted to a particular queue. This is given
the credentials from the event generator (which may be the system) and
the watch setter. [Wanted by Smack]
I've provided SELinux and Smack with implementations of some of these hooks.
Why:
(1) Key/keyring notifications.
If you have your kerberos tickets in a file/directory, your gnome desktop
will monitor that using something like fanotify and tell you if your
credentials cache changes.
We also have the ability to cache your kerberos tickets in the session,
user or persistent keyring so that it isn't left around on disk across a
reboot or logout. Keyrings, however, cannot currently be monitored
asynchronously, so the desktop has to poll for it - not so good on a
laptop.
This source will allow the desktop to avoid the need to poll.
(2) USB notifications.
GregKH was looking for a way to do USB notifications as I was looking to
find additional sources to implement. I'm not sure how he wants to use
them, but I'll let him speak to that himself.
(3) Block notifications.
This one I was thinking that I could make something like ddrescue better
by letting it get notifications this way. This was a target of
convenience since I had a dodgy disk I was trying to rescue.
It could also potentially be used help systemd, say, detect broken
devices and avoid trying to unmount them when trying to reboot the machine.
I can drop this for now if you prefer.
(4) Mount notifications.
This one is wanted to avoid repeated trawling of /proc/mounts or similar
to work out changes to the mount object attributes and mount topology.
I'm told that the proc file holding the namespace_sem is a point of
contention, especially as the process of generating the text descriptions
of the mounts/superblocks can be quite involved.
The notifications directly indicate the mounts involved in any particular
event and what the change was. You can poll /proc/mounts, but all you
know is that something changed; you don't know what and you don't know
how and reading that file may race with multiple changed being effected.
I pair this with a new fsinfo() system call that allows, amongst other
things, the ability to retrieve in one go an { id, change counter } tuple
from all the children of a specified mount, allowing buffer overruns to
be cleaned up quickly.
It's not just Red Hat that's potentially interested in this:
https://lore.kernel.org/linux-fsdevel/[email protected]/
(5) Superblock notifications.
This one is provided to allow systemd or the desktop to more easily
detect events such as I/O errors and EDQUOT/ENOSPC.
Design decisions:
(1) The notification queue is built on top of a standard pipe. Messages
are effectively spliced in. The pipe is opened with a special flag:
pipe2(fds, O_NOTIFICATION_PIPE);
The special flag has the same value as O_EXCL (which doesn't seem like
it will ever be applicable in this context)[?]. It is given up front
to make it a lot easier to prohibit splice and co. from accessing the
pipe.
[?] Should this be done some other way? I'd rather not use up a new
O_* flag if I can avoid it - should I add a pipe3() system call
instead?
The pipe is then configured::
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
Messages are then read out of the pipe using read().
(2) It should be possible to allow write() to insert data into the
notification pipes too, but this is currently disabled as the kernel
has to be able to insert messages into the pipe *without* holding
pipe->mutex and the code to make this work needs careful auditing.
(3) sendfile(), splice() and vmsplice() are disabled on notification pipes
because of the pipe->mutex issue and also because they sometimes want
to revert what they just did - but one or more notification messages
might've been interleaved in the ring.
(4) The kernel inserts messages with the wait queue spinlock held. This
means that pipe_read() and pipe_write() have to take the spinlock to
update the queue pointers.
(5) Records in the buffer are binary, typed and have a length so that they
can be of varying size.
This allows multiple heterogeneous sources to share a common buffer;
there are 16 million types available, of which I've used just a few,
so there is scope for others to be used. Tags may be specified when a
watchpoint is created to help distinguish the sources.
(6) Records are filterable as types have up to 256 subtypes that can be
individually filtered. Other filtration is also available.
(7) Notification pipes don't interfere with each other; each may be bound
to a different set of watches. Any particular notification will be
copied to all the queues that are currently watching for it - and only
those that are watching for it.
(8) When recording a notification, the kernel will not sleep, but will
rather mark a queue as having lost a message if there's insufficient
space. read() will fabricate a loss notification message at an
appropriate point later.
(9) The notification pipe is created and then watchpoints are attached to
it, using one of:
keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
watch_devices(fds[1], 0x02, 0);
where in both cases, fd indicates the queue and the number after is a
tag between 0 and 255.
(10) Watches are removed if either the notification pipe is destroyed or
the watched object is destroyed. In the latter case, a message will
be generated indicating the enforced watch removal.
Things I want to avoid:
(1) Introducing features that make the core VFS dependent on the network
stack or networking namespaces (ie. usage of netlink).
(2) Dumping all this stuff into dmesg and having a daemon that sits there
parsing the output and distributing it as this then puts the
responsibility for security into userspace and makes handling
namespaces tricky. Further, dmesg might not exist or might be
inaccessible inside a container.
(3) Letting users see events they shouldn't be able to see.
Testing and manpages:
(*) The keyutils tree has a pipe-watch branch that has keyctl commands for
making use of notifications. Proposed manual pages can also be found
on this branch, though a couple of them really need to go to the main
manpages repository instead.
If the kernel supports the watching of keys, then running "make test"
on that branch will cause the testing infrastructure to spawn a
monitoring process on the side that monitors a notifications pipe for
all the key/keyring changes induced by the tests and they'll all be
checked off to make sure they happened.
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=pipe-watch
(*) A test program is provided (samples/watch_queue/watch_test) that can
be used to monitor for keyrings, some USB and some block device
events. Information on the notifications is simply logged to stdout.
The kernel patches can also be found here:
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=notifications-pipe-core
Changes:
ver #3:
(*) Rebase to after latest upstream pipe patches.
(*) Fix a missing ref get in add_watch_to_object().
ver #2:
(*) Declare O_NOTIFICATION_PIPE to use and switch it to be the same value
as O_EXCL rather then O_TMPFILE (the latter is a bit nasty in its
implementation).
ver #1:
(*) Build on top of standard pipes instead of having a driver.
David
---
David Howells (14):
uapi: General notification queue definitions
security: Add hooks to rule on setting a watch
security: Add a hook for the point of notification insertion
pipe: Add O_NOTIFICATION_PIPE
pipe: Add general notification queue support
keys: Add a notification facility
Add sample notification program
pipe: Allow buffers to be marked read-whole-or-error for notifications
pipe: Add notification lossage handling
Add a general, global device notification watch list
block: Add block layer notifications
usb: Add USB subsystem notifications
selinux: Implement the watch_key security hook
smack: Implement the watch_key and post_notification hooks
Documentation/security/keys/core.rst | 58 ++
Documentation/userspace-api/ioctl/ioctl-number.rst | 1
Documentation/watch_queue.rst | 385 ++++++++++++
arch/alpha/kernel/syscalls/syscall.tbl | 1
arch/arm/tools/syscall.tbl | 1
arch/arm64/include/asm/unistd.h | 2
arch/arm64/include/asm/unistd32.h | 2
arch/ia64/kernel/syscalls/syscall.tbl | 1
arch/m68k/kernel/syscalls/syscall.tbl | 1
arch/microblaze/kernel/syscalls/syscall.tbl | 1
arch/mips/kernel/syscalls/syscall_n32.tbl | 1
arch/mips/kernel/syscalls/syscall_n64.tbl | 1
arch/mips/kernel/syscalls/syscall_o32.tbl | 1
arch/parisc/kernel/syscalls/syscall.tbl | 1
arch/powerpc/kernel/syscalls/syscall.tbl | 1
arch/s390/kernel/syscalls/syscall.tbl | 1
arch/sh/kernel/syscalls/syscall.tbl | 1
arch/sparc/kernel/syscalls/syscall.tbl | 1
arch/x86/entry/syscalls/syscall_32.tbl | 1
arch/x86/entry/syscalls/syscall_64.tbl | 1
arch/xtensa/kernel/syscalls/syscall.tbl | 1
block/Kconfig | 9
block/blk-core.c | 29 +
drivers/base/Kconfig | 9
drivers/base/Makefile | 1
drivers/base/watch.c | 90 +++
drivers/usb/core/Kconfig | 9
drivers/usb/core/devio.c | 47 +
drivers/usb/core/hub.c | 4
fs/pipe.c | 242 +++++--
fs/splice.c | 12
include/linux/blkdev.h | 15
include/linux/device.h | 7
include/linux/key.h | 3
include/linux/lsm_audit.h | 1
include/linux/lsm_hooks.h | 38 +
include/linux/pipe_fs_i.h | 27 +
include/linux/security.h | 31 +
include/linux/syscalls.h | 1
include/linux/usb.h | 18 +
include/linux/watch_queue.h | 127 ++++
include/uapi/asm-generic/unistd.h | 4
include/uapi/linux/keyctl.h | 2
include/uapi/linux/watch_queue.h | 158 +++++
init/Kconfig | 12
kernel/Makefile | 1
kernel/sys_ni.c | 1
kernel/watch_queue.c | 659 ++++++++++++++++++++
samples/Kconfig | 6
samples/Makefile | 1
samples/watch_queue/Makefile | 7
samples/watch_queue/watch_test.c | 251 ++++++++
security/keys/Kconfig | 9
security/keys/compat.c | 3
security/keys/gc.c | 5
security/keys/internal.h | 30 +
security/keys/key.c | 38 +
security/keys/keyctl.c | 99 +++
security/keys/keyring.c | 20 -
security/keys/request_key.c | 4
security/security.c | 23 +
security/selinux/hooks.c | 14
security/smack/smack_lsm.c | 82 ++
63 files changed, 2506 insertions(+), 107 deletions(-)
create mode 100644 Documentation/watch_queue.rst
create mode 100644 drivers/base/watch.c
create mode 100644 include/linux/watch_queue.h
create mode 100644 include/uapi/linux/watch_queue.h
create mode 100644 kernel/watch_queue.c
create mode 100644 samples/watch_queue/Makefile
create mode 100644 samples/watch_queue/watch_test.c
Add security hooks that will allow an LSM to rule on whether or not a watch
may be set. More than one hook is required as the watches watch different
types of object.
Signed-off-by: David Howells <[email protected]>
cc: Casey Schaufler <[email protected]>
cc: Stephen Smalley <[email protected]>
cc: [email protected]
---
include/linux/lsm_hooks.h | 24 ++++++++++++++++++++++++
include/linux/security.h | 17 +++++++++++++++++
security/security.c | 14 ++++++++++++++
3 files changed, 55 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 20d8cf194fb7..79d7c73676d7 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1416,6 +1416,18 @@
* @ctx is a pointer in which to place the allocated security context.
* @ctxlen points to the place to put the length of @ctx.
*
+ * Security hooks for the general notification queue:
+ *
+ * @watch_key:
+ * Check to see if a process is allowed to watch for event notifications
+ * from a key or keyring.
+ * @key: The key to watch.
+ *
+ * @watch_devices:
+ * Check to see if a process is allowed to watch for event notifications
+ * from devices (as a global set).
+ *
+ *
* Security hooks for using the eBPF maps and programs functionalities through
* eBPF syscalls.
*
@@ -1698,6 +1710,12 @@ union security_list_options {
int (*inode_notifysecctx)(struct inode *inode, void *ctx, u32 ctxlen);
int (*inode_setsecctx)(struct dentry *dentry, void *ctx, u32 ctxlen);
int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ int (*watch_key)(struct key *key);
+#endif
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+ int (*watch_devices)(void);
+#endif
#ifdef CONFIG_SECURITY_NETWORK
int (*unix_stream_connect)(struct sock *sock, struct sock *other,
@@ -1985,6 +2003,12 @@ struct security_hook_heads {
struct hlist_head inode_notifysecctx;
struct hlist_head inode_setsecctx;
struct hlist_head inode_getsecctx;
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ struct hlist_head watch_key;
+#endif
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+ struct hlist_head watch_devices;
+#endif
#ifdef CONFIG_SECURITY_NETWORK
struct hlist_head unix_stream_connect;
struct hlist_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index 3e8d4bacd59d..8f2fa100d128 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1274,6 +1274,23 @@ static inline int security_locked_down(enum lockdown_reason what)
}
#endif /* CONFIG_SECURITY */
+#if defined(CONFIG_SECURITY) && defined(CONFIG_KEY_NOTIFICATIONS)
+int security_watch_key(struct key *key);
+#else
+static inline int security_watch_key(struct key *key)
+{
+ return 0;
+}
+#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_DEVICE_NOTIFICATIONS)
+int security_watch_devices(void);
+#else
+static inline int security_watch_devices(void)
+{
+ return 0;
+}
+#endif
+
#ifdef CONFIG_SECURITY_NETWORK
int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk);
diff --git a/security/security.c b/security/security.c
index cd2d18d2d279..578863f230a6 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1956,6 +1956,20 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
}
EXPORT_SYMBOL(security_inode_getsecctx);
+#ifdef CONFIG_KEY_NOTIFICATIONS
+int security_watch_key(struct key *key)
+{
+ return call_int_hook(watch_key, 0, key);
+}
+#endif
+
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+int security_watch_devices(void)
+{
+ return call_int_hook(watch_devices, 0);
+}
+#endif
+
#ifdef CONFIG_SECURITY_NETWORK
int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk)
Add a security hook that allows an LSM to rule on whether a notification
message is allowed to be inserted into a particular watch queue.
The hook is given the following information:
(1) The credentials of the triggerer (which may be init_cred for a system
notification, eg. a hardware error).
(2) The credentials of the whoever set the watch.
(3) The notification message.
Signed-off-by: David Howells <[email protected]>
cc: Casey Schaufler <[email protected]>
cc: Stephen Smalley <[email protected]>
cc: [email protected]
---
include/linux/lsm_hooks.h | 14 ++++++++++++++
include/linux/security.h | 14 ++++++++++++++
security/security.c | 9 +++++++++
3 files changed, 37 insertions(+)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 79d7c73676d7..16530255dc11 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1427,6 +1427,12 @@
* Check to see if a process is allowed to watch for event notifications
* from devices (as a global set).
*
+ * @post_notification:
+ * Check to see if a watch notification can be posted to a particular
+ * queue.
+ * @w_cred: The credentials of the whoever set the watch.
+ * @cred: The event-triggerer's credentials
+ * @n: The notification being posted
*
* Security hooks for using the eBPF maps and programs functionalities through
* eBPF syscalls.
@@ -1716,6 +1722,11 @@ union security_list_options {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int (*watch_devices)(void);
#endif
+#ifdef CONFIG_WATCH_QUEUE
+ int (*post_notification)(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
+#endif
#ifdef CONFIG_SECURITY_NETWORK
int (*unix_stream_connect)(struct sock *sock, struct sock *other,
@@ -2009,6 +2020,9 @@ struct security_hook_heads {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
struct hlist_head watch_devices;
#endif
+#ifdef CONFIG_WATCH_QUEUE
+ struct hlist_head post_notification;
+#endif /* CONFIG_WATCH_QUEUE */
#ifdef CONFIG_SECURITY_NETWORK
struct hlist_head unix_stream_connect;
struct hlist_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index 8f2fa100d128..e03ee1164268 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -57,6 +57,8 @@ struct mm_struct;
struct fs_context;
struct fs_parameter;
enum fs_value_type;
+struct watch;
+struct watch_notification;
/* Default (no) options for the capable function */
#define CAP_OPT_NONE 0x0
@@ -1290,6 +1292,18 @@ static inline int security_watch_devices(void)
return 0;
}
#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
+int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
+#else
+static inline int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return 0;
+}
+#endif
#ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/security.c b/security/security.c
index 578863f230a6..9c1878a7fadf 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1956,6 +1956,15 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
}
EXPORT_SYMBOL(security_inode_getsecctx);
+#ifdef CONFIG_WATCH_QUEUE
+int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return call_int_hook(post_notification, 0, w_cred, cred, n);
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
#ifdef CONFIG_KEY_NOTIFICATIONS
int security_watch_key(struct key *key)
{
Add an O_NOTIFICATION_PIPE flag that can be passed to pipe2() to indicate
that the pipe being created is going to be used for notifications. This
suppresses the use of splice(), vmsplice(), tee() and sendfile() on the
pipe as calling iov_iter_revert() on a pipe when a kernel notification
message has been inserted into the middle of a multi-buffer splice will be
messy.
The flag is given the same value as O_EXCL as it seems unlikely that
this flag will ever be applicable to pipes and I don't want to use up
another O_* bit unnecessarily. An alternative could be to add a pipe3()
system call.
Signed-off-by: David Howells <[email protected]>
---
include/uapi/linux/watch_queue.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 5f3d21e8a34b..9df72227f515 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -3,6 +3,9 @@
#define _UAPI_LINUX_WATCH_QUEUE_H
#include <linux/types.h>
+#include <linux/fcntl.h>
+
+#define O_NOTIFICATION_PIPE O_EXCL /* Parameter to pipe2() selecting notification pipe */
enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
Add a key/keyring change notification facility whereby notifications about
changes in key and keyring content and attributes can be received.
Firstly, an event queue needs to be created:
pipe2(fds, O_NOTIFICATION_PIPE);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
then a notification can be set up to report notifications via that queue:
struct watch_notification_filter filter = {
.nr_filters = 1,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
After that, records will be placed into the queue when events occur in
which keys are changed in some way. Records are of the following format:
struct key_notification {
struct watch_notification watch;
__u32 key_id;
__u32 aux;
} *n;
Where:
n->watch.type will be WATCH_TYPE_KEY_NOTIFY.
n->watch.subtype will indicate the type of event, such as
NOTIFY_KEY_REVOKED.
n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
record.
n->watch.info & WATCH_INFO_ID will be the second argument to
keyctl_watch_key(), shifted.
n->key will be the ID of the affected key.
n->aux will hold subtype-dependent information, such as the key
being linked into the keyring specified by n->key in the case of
NOTIFY_KEY_LINKED.
Note that it is permissible for event records to be of variable length -
or, at least, the length may be dependent on the subtype. Note also that
the queue can be shared between multiple notifications of various types.
Signed-off-by: David Howells <[email protected]>
---
Documentation/security/keys/core.rst | 58 ++++++++++++++++++++
include/linux/key.h | 3 +
include/uapi/linux/keyctl.h | 2 +
include/uapi/linux/watch_queue.h | 28 +++++++++-
security/keys/Kconfig | 9 +++
security/keys/compat.c | 3 +
security/keys/gc.c | 5 ++
security/keys/internal.h | 30 ++++++++++
security/keys/key.c | 38 ++++++++-----
security/keys/keyctl.c | 99 +++++++++++++++++++++++++++++++++-
security/keys/keyring.c | 20 ++++---
security/keys/request_key.c | 4 +
12 files changed, 271 insertions(+), 28 deletions(-)
diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
index d9b0b859018b..0154721b20b2 100644
--- a/Documentation/security/keys/core.rst
+++ b/Documentation/security/keys/core.rst
@@ -833,6 +833,7 @@ The keyctl syscall functions are:
A process must have search permission on the key for this function to be
successful.
+
* Compute a Diffie-Hellman shared secret or public key::
long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params,
@@ -1026,6 +1027,63 @@ The keyctl syscall functions are:
written into the output buffer. Verification returns 0 on success.
+ * Watch a key or keyring for changes::
+
+ long keyctl(KEYCTL_WATCH_KEY, key_serial_t key, int queue_fd,
+ const struct watch_notification_filter *filter);
+
+ This will set or remove a watch for changes on the specified key or
+ keyring.
+
+ "key" is the ID of the key to be watched.
+
+ "queue_fd" is a file descriptor referring to an open "/dev/watch_queue"
+ which manages the buffer into which notifications will be delivered.
+
+ "filter" is either NULL to remove a watch or a filter specification to
+ indicate what events are required from the key.
+
+ See Documentation/watch_queue.rst for more information.
+
+ Note that only one watch may be emplaced for any particular { key,
+ queue_fd } combination.
+
+ Notification records look like::
+
+ struct key_notification {
+ struct watch_notification watch;
+ __u32 key_id;
+ __u32 aux;
+ };
+
+ In this, watch::type will be "WATCH_TYPE_KEY_NOTIFY" and subtype will be
+ one of::
+
+ NOTIFY_KEY_INSTANTIATED
+ NOTIFY_KEY_UPDATED
+ NOTIFY_KEY_LINKED
+ NOTIFY_KEY_UNLINKED
+ NOTIFY_KEY_CLEARED
+ NOTIFY_KEY_REVOKED
+ NOTIFY_KEY_INVALIDATED
+ NOTIFY_KEY_SETATTR
+
+ Where these indicate a key being instantiated/rejected, updated, a link
+ being made in a keyring, a link being removed from a keyring, a keyring
+ being cleared, a key being revoked, a key being invalidated or a key
+ having one of its attributes changed (user, group, perm, timeout,
+ restriction).
+
+ If a watched key is deleted, a basic watch_notification will be issued
+ with "type" set to WATCH_TYPE_META and "subtype" set to
+ watch_meta_removal_notification. The watchpoint ID will be set in the
+ "info" field.
+
+ This needs to be configured by enabling:
+
+ "Provide key/keyring change notifications" (KEY_NOTIFICATIONS)
+
+
Kernel Services
===============
diff --git a/include/linux/key.h b/include/linux/key.h
index 6cf8e71cf8b7..b99b40db08fc 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -176,6 +176,9 @@ struct key {
struct list_head graveyard_link;
struct rb_node serial_node;
};
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ struct watch_list *watchers; /* Entities watching this key for changes */
+#endif
struct rw_semaphore sem; /* change vs change sem */
struct key_user *user; /* owner of this key */
void *security; /* security data for this key */
diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index ed3d5893830d..4c8884eea808 100644
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -69,6 +69,7 @@
#define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */
#define KEYCTL_MOVE 30 /* Move keys between keyrings */
#define KEYCTL_CAPABILITIES 31 /* Find capabilities of keyrings subsystem */
+#define KEYCTL_WATCH_KEY 32 /* Watch a key or ring of keys for changes */
/* keyctl structures */
struct keyctl_dh_params {
@@ -130,5 +131,6 @@ struct keyctl_pkey_params {
#define KEYCTL_CAPS0_MOVE 0x80 /* KEYCTL_MOVE supported */
#define KEYCTL_CAPS1_NS_KEYRING_NAME 0x01 /* Keyring names are per-user_namespace */
#define KEYCTL_CAPS1_NS_KEY_TAG 0x02 /* Key indexing can include a namespace tag */
+#define KEYCTL_CAPS1_NOTIFICATIONS 0x04 /* Keys generate watchable notifications */
#endif /* _LINUX_KEYCTL_H */
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 3a5790f1f05d..c3d8320b5d3a 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -13,7 +13,8 @@
enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
- WATCH_TYPE__NR = 1
+ WATCH_TYPE_KEY_NOTIFY = 1, /* Key change event notification */
+ WATCH_TYPE__NR = 2
};
enum watch_meta_notification_subtype {
@@ -75,4 +76,29 @@ struct watch_notification_removal {
__u64 id; /* Type-dependent identifier */
};
+/*
+ * Type of key/keyring change notification.
+ */
+enum key_notification_subtype {
+ NOTIFY_KEY_INSTANTIATED = 0, /* Key was instantiated (aux is error code) */
+ NOTIFY_KEY_UPDATED = 1, /* Key was updated */
+ NOTIFY_KEY_LINKED = 2, /* Key (aux) was added to watched keyring */
+ NOTIFY_KEY_UNLINKED = 3, /* Key (aux) was removed from watched keyring */
+ NOTIFY_KEY_CLEARED = 4, /* Keyring was cleared */
+ NOTIFY_KEY_REVOKED = 5, /* Key was revoked */
+ NOTIFY_KEY_INVALIDATED = 6, /* Key was invalidated */
+ NOTIFY_KEY_SETATTR = 7, /* Key's attributes got changed */
+};
+
+/*
+ * Key/keyring notification record.
+ * - watch.type = WATCH_TYPE_KEY_NOTIFY
+ * - watch.subtype = enum key_notification_type
+ */
+struct key_notification {
+ struct watch_notification watch;
+ __u32 key_id; /* The key/keyring affected */
+ __u32 aux; /* Per-type auxiliary data */
+};
+
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 47c041563d41..d4dc5ea208af 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -116,3 +116,12 @@ config KEY_DH_OPERATIONS
in the kernel.
If you are unsure as to whether this is required, answer N.
+
+config KEY_NOTIFICATIONS
+ bool "Provide key/keyring change notifications"
+ depends on KEYS && WATCH_QUEUE
+ help
+ This option provides support for getting change notifications on keys
+ and keyrings on which the caller has View permission. This makes use
+ of the /dev/watch_queue misc device to handle the notification
+ buffer and provides KEYCTL_WATCH_KEY to enable/disable watches.
diff --git a/security/keys/compat.c b/security/keys/compat.c
index b975f8f11124..6ee9d8f6a4a5 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -156,6 +156,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
case KEYCTL_CAPABILITIES:
return keyctl_capabilities(compat_ptr(arg2), arg3);
+ case KEYCTL_WATCH_KEY:
+ return keyctl_watch_key(arg2, arg3, arg4);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 671dd730ecfc..3c90807476eb 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -131,6 +131,11 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
kdebug("- %u", key->serial);
key_check(key);
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ remove_watch_list(key->watchers, key->serial);
+ key->watchers = NULL;
+#endif
+
/* Throw away the key data if the key is instantiated */
if (state == KEY_IS_POSITIVE && key->type->destroy)
key->type->destroy(key);
diff --git a/security/keys/internal.h b/security/keys/internal.h
index ba3e2da14cef..2a230c665162 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -15,6 +15,7 @@
#include <linux/task_work.h>
#include <linux/keyctl.h>
#include <linux/refcount.h>
+#include <linux/watch_queue.h>
#include <linux/compat.h>
struct iovec;
@@ -97,7 +98,8 @@ extern int __key_link_begin(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit **_edit);
extern int __key_link_check_live_key(struct key *keyring, struct key *key);
-extern void __key_link(struct key *key, struct assoc_array_edit **_edit);
+extern void __key_link(struct key *keyring, struct key *key,
+ struct assoc_array_edit **_edit);
extern void __key_link_end(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit *edit);
@@ -181,6 +183,23 @@ extern int key_task_permission(const key_ref_t key_ref,
const struct cred *cred,
key_perm_t perm);
+static inline void notify_key(struct key *key,
+ enum key_notification_subtype subtype, u32 aux)
+{
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ struct key_notification n = {
+ .watch.type = WATCH_TYPE_KEY_NOTIFY,
+ .watch.subtype = subtype,
+ .watch.info = watch_sizeof(n),
+ .key_id = key_serial(key),
+ .aux = aux,
+ };
+
+ post_watch_notification(key->watchers, &n.watch, current_cred(),
+ n.key_id);
+#endif
+}
+
/*
* Check to see whether permission is granted to use a key in the desired way.
*/
@@ -331,6 +350,15 @@ static inline long keyctl_pkey_e_d_s(int op,
extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen);
+#ifdef CONFIG_KEY_NOTIFICATIONS
+extern long keyctl_watch_key(key_serial_t, int, int);
+#else
+static inline long keyctl_watch_key(key_serial_t key_id, int watch_fd, int watch_id)
+{
+ return -EOPNOTSUPP;
+}
+#endif
+
/*
* Debugging key validation
*/
diff --git a/security/keys/key.c b/security/keys/key.c
index 764f4c57913e..83e8d7c4bb6f 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -443,6 +443,7 @@ static int __key_instantiate_and_link(struct key *key,
/* mark the key as being instantiated */
atomic_inc(&key->user->nikeys);
mark_key_instantiated(key, 0);
+ notify_key(key, NOTIFY_KEY_INSTANTIATED, 0);
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
@@ -452,7 +453,7 @@ static int __key_instantiate_and_link(struct key *key,
if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
set_bit(KEY_FLAG_KEEP, &key->flags);
- __key_link(key, _edit);
+ __key_link(keyring, key, _edit);
}
/* disable the authorisation key */
@@ -600,6 +601,7 @@ int key_reject_and_link(struct key *key,
/* mark the key as being negatively instantiated */
atomic_inc(&key->user->nikeys);
mark_key_instantiated(key, -error);
+ notify_key(key, NOTIFY_KEY_INSTANTIATED, -error);
key->expiry = ktime_get_real_seconds() + timeout;
key_schedule_gc(key->expiry + key_gc_delay);
@@ -610,7 +612,7 @@ int key_reject_and_link(struct key *key,
/* and link it into the destination keyring */
if (keyring && link_ret == 0)
- __key_link(key, &edit);
+ __key_link(keyring, key, &edit);
/* disable the authorisation key */
if (authkey)
@@ -763,9 +765,11 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
down_write(&key->sem);
ret = key->type->update(key, prep);
- if (ret == 0)
+ if (ret == 0) {
/* Updating a negative key positively instantiates it */
mark_key_instantiated(key, 0);
+ notify_key(key, NOTIFY_KEY_UPDATED, 0);
+ }
up_write(&key->sem);
@@ -1013,9 +1017,11 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
down_write(&key->sem);
ret = key->type->update(key, &prep);
- if (ret == 0)
+ if (ret == 0) {
/* Updating a negative key positively instantiates it */
mark_key_instantiated(key, 0);
+ notify_key(key, NOTIFY_KEY_UPDATED, 0);
+ }
up_write(&key->sem);
@@ -1047,15 +1053,17 @@ void key_revoke(struct key *key)
* instantiated
*/
down_write_nested(&key->sem, 1);
- if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
- key->type->revoke)
- key->type->revoke(key);
-
- /* set the death time to no more than the expiry time */
- time = ktime_get_real_seconds();
- if (key->revoked_at == 0 || key->revoked_at > time) {
- key->revoked_at = time;
- key_schedule_gc(key->revoked_at + key_gc_delay);
+ if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags)) {
+ notify_key(key, NOTIFY_KEY_REVOKED, 0);
+ if (key->type->revoke)
+ key->type->revoke(key);
+
+ /* set the death time to no more than the expiry time */
+ time = ktime_get_real_seconds();
+ if (key->revoked_at == 0 || key->revoked_at > time) {
+ key->revoked_at = time;
+ key_schedule_gc(key->revoked_at + key_gc_delay);
+ }
}
up_write(&key->sem);
@@ -1077,8 +1085,10 @@ void key_invalidate(struct key *key)
if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
down_write_nested(&key->sem, 1);
- if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
+ if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
+ notify_key(key, NOTIFY_KEY_INVALIDATED, 0);
key_schedule_gc_links();
+ }
up_write(&key->sem);
}
}
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 9b898c969558..6610649514fb 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -37,7 +37,9 @@ static const unsigned char keyrings_capabilities[2] = {
KEYCTL_CAPS0_MOVE
),
[1] = (KEYCTL_CAPS1_NS_KEYRING_NAME |
- KEYCTL_CAPS1_NS_KEY_TAG),
+ KEYCTL_CAPS1_NS_KEY_TAG |
+ (IS_ENABLED(CONFIG_KEY_NOTIFICATIONS) ? KEYCTL_CAPS1_NOTIFICATIONS : 0)
+ ),
};
static int key_get_type_from_user(char *type,
@@ -970,6 +972,7 @@ long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
if (group != (gid_t) -1)
key->gid = gid;
+ notify_key(key, NOTIFY_KEY_SETATTR, 0);
ret = 0;
error_put:
@@ -1020,6 +1023,7 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
/* if we're not the sysadmin, we can only change a key that we own */
if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
key->perm = perm;
+ notify_key(key, NOTIFY_KEY_SETATTR, 0);
ret = 0;
}
@@ -1411,10 +1415,12 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
okay:
key = key_ref_to_ptr(key_ref);
ret = 0;
- if (test_bit(KEY_FLAG_KEEP, &key->flags))
+ if (test_bit(KEY_FLAG_KEEP, &key->flags)) {
ret = -EPERM;
- else
+ } else {
key_set_timeout(key, timeout);
+ notify_key(key, NOTIFY_KEY_SETATTR, 0);
+ }
key_put(key);
error:
@@ -1688,6 +1694,90 @@ long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
return ret;
}
+#ifdef CONFIG_KEY_NOTIFICATIONS
+/*
+ * Watch for changes to a key.
+ *
+ * The caller must have View permission to watch a key or keyring.
+ */
+long keyctl_watch_key(key_serial_t id, int watch_queue_fd, int watch_id)
+{
+ struct watch_queue *wqueue;
+ struct watch_list *wlist = NULL;
+ struct watch *watch = NULL;
+ struct key *key;
+ key_ref_t key_ref;
+ long ret;
+
+ if (watch_id < -1 || watch_id > 0xff)
+ return -EINVAL;
+
+ key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_VIEW);
+ if (IS_ERR(key_ref))
+ return PTR_ERR(key_ref);
+ key = key_ref_to_ptr(key_ref);
+
+ wqueue = get_watch_queue(watch_queue_fd);
+ if (IS_ERR(wqueue)) {
+ ret = PTR_ERR(wqueue);
+ goto err_key;
+ }
+
+ if (watch_id >= 0) {
+ ret = -ENOMEM;
+ if (!key->watchers) {
+ wlist = kzalloc(sizeof(*wlist), GFP_KERNEL);
+ if (!wlist)
+ goto err_wqueue;
+ init_watch_list(wlist, NULL);
+ }
+
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (!watch)
+ goto err_wlist;
+
+ init_watch(watch, wqueue);
+ watch->id = key->serial;
+ watch->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+ ret = security_watch_key(key);
+ if (ret < 0)
+ goto err_watch;
+
+ down_write(&key->sem);
+ if (!key->watchers) {
+ key->watchers = wlist;
+ wlist = NULL;
+ }
+
+ ret = add_watch_to_object(watch, key->watchers);
+ up_write(&key->sem);
+
+ if (ret == 0)
+ watch = NULL;
+ } else {
+ ret = -EBADSLT;
+ if (key->watchers) {
+ down_write(&key->sem);
+ ret = remove_watch_from_object(key->watchers,
+ wqueue, key_serial(key),
+ false);
+ up_write(&key->sem);
+ }
+ }
+
+err_watch:
+ kfree(watch);
+err_wlist:
+ kfree(wlist);
+err_wqueue:
+ put_watch_queue(wqueue);
+err_key:
+ key_put(key);
+ return ret;
+}
+#endif /* CONFIG_KEY_NOTIFICATIONS */
+
/*
* Get keyrings subsystem capabilities.
*/
@@ -1857,6 +1947,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
case KEYCTL_CAPABILITIES:
return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);
+ case KEYCTL_WATCH_KEY:
+ return keyctl_watch_key((key_serial_t)arg2, (int)arg3, (int)arg4);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index febf36c6ddc5..40a0dcdfda44 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1060,12 +1060,14 @@ int keyring_restrict(key_ref_t keyring_ref, const char *type,
down_write(&keyring->sem);
down_write(&keyring_serialise_restrict_sem);
- if (keyring->restrict_link)
+ if (keyring->restrict_link) {
ret = -EEXIST;
- else if (keyring_detect_restriction_cycle(keyring, restrict_link))
+ } else if (keyring_detect_restriction_cycle(keyring, restrict_link)) {
ret = -EDEADLK;
- else
+ } else {
keyring->restrict_link = restrict_link;
+ notify_key(keyring, NOTIFY_KEY_SETATTR, 0);
+ }
up_write(&keyring_serialise_restrict_sem);
up_write(&keyring->sem);
@@ -1366,12 +1368,14 @@ int __key_link_check_live_key(struct key *keyring, struct key *key)
* holds at most one link to any given key of a particular type+description
* combination.
*/
-void __key_link(struct key *key, struct assoc_array_edit **_edit)
+void __key_link(struct key *keyring, struct key *key,
+ struct assoc_array_edit **_edit)
{
__key_get(key);
assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
assoc_array_apply_edit(*_edit);
*_edit = NULL;
+ notify_key(keyring, NOTIFY_KEY_LINKED, key_serial(key));
}
/*
@@ -1455,7 +1459,7 @@ int key_link(struct key *keyring, struct key *key)
if (ret == 0)
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
- __key_link(key, &edit);
+ __key_link(keyring, key, &edit);
error_end:
__key_link_end(keyring, &key->index_key, edit);
@@ -1487,7 +1491,7 @@ static int __key_unlink_begin(struct key *keyring, struct key *key,
struct assoc_array_edit *edit;
BUG_ON(*_edit != NULL);
-
+
edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
&key->index_key);
if (IS_ERR(edit))
@@ -1507,6 +1511,7 @@ static void __key_unlink(struct key *keyring, struct key *key,
struct assoc_array_edit **_edit)
{
assoc_array_apply_edit(*_edit);
+ notify_key(keyring, NOTIFY_KEY_UNLINKED, key_serial(key));
*_edit = NULL;
key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
}
@@ -1625,7 +1630,7 @@ int key_move(struct key *key,
goto error;
__key_unlink(from_keyring, key, &from_edit);
- __key_link(key, &to_edit);
+ __key_link(to_keyring, key, &to_edit);
error:
__key_link_end(to_keyring, &key->index_key, to_edit);
__key_unlink_end(from_keyring, key, from_edit);
@@ -1659,6 +1664,7 @@ int keyring_clear(struct key *keyring)
} else {
if (edit)
assoc_array_apply_edit(edit);
+ notify_key(keyring, NOTIFY_KEY_CLEARED, 0);
key_payload_reserve(keyring, 0);
ret = 0;
}
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 957b9e3e1492..e1b9f1a80676 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -418,7 +418,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
goto key_already_present;
if (dest_keyring)
- __key_link(key, &edit);
+ __key_link(dest_keyring, key, &edit);
mutex_unlock(&key_construction_mutex);
if (dest_keyring)
@@ -437,7 +437,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx,
if (dest_keyring) {
ret = __key_link_check_live_key(dest_keyring, key);
if (ret == 0)
- __key_link(key, &edit);
+ __key_link(dest_keyring, key, &edit);
__key_link_end(dest_keyring, &ctx->index_key, edit);
if (ret < 0)
goto link_check_failed;
Make it possible to have a general notification queue built on top of a
standard pipe. Notifications are 'spliced' into the pipe and then read
out. splice(), vmsplice() and sendfile() are forbidden on pipes used for
notifications as post_one_notification() cannot take pipe->mutex. This
means that notifications could be posted in between individual pipe
buffers, making iov_iter_revert() difficult to effect.
The way the notification queue is used is:
(1) An application opens a pipe with a special flag and indicates the
number of messages it wishes to be able to queue at once (this can
only be set once):
pipe2(fds, O_NOTIFICATION_PIPE);
ioctl(fds[0], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);
(2) The application then uses poll() and read() as normal to extract data
from the pipe. read() will return multiple notifications if the
buffer is big enough, but it will not split a notification across
buffers - rather it will return a short read or EMSGSIZE.
Notification messages include a length in the header so that the
caller can split them up.
Each message has a header that describes it:
struct watch_notification {
__u32 type:24;
__u32 subtype:8;
__u32 info;
};
The type indicates the source (eg. mount tree changes, superblock events,
keyring changes, block layer events) and the subtype indicates the event
type (eg. mount, unmount; EIO, EDQUOT; link, unlink). The info field
indicates a number of things, including the entry length, an ID assigned to
a watchpoint contributing to this buffer and type-specific flags.
Supplementary data, such as the key ID that generated an event, can be
attached in additional slots. The maximum message size is 127 bytes.
Messages may not be padded or aligned, so there is no guarantee, for
example, that the notification type will be on a 4-byte bounary.
Signed-off-by: David Howells <[email protected]>
---
Documentation/userspace-api/ioctl/ioctl-number.rst | 1
Documentation/watch_queue.rst | 354 +++++++++++
fs/pipe.c | 206 ++++--
fs/splice.c | 12
include/linux/pipe_fs_i.h | 19 +
include/linux/watch_queue.h | 127 ++++
include/uapi/linux/watch_queue.h | 20 +
init/Kconfig | 12
kernel/Makefile | 1
kernel/watch_queue.c | 657 ++++++++++++++++++++
10 files changed, 1333 insertions(+), 76 deletions(-)
create mode 100644 Documentation/watch_queue.rst
create mode 100644 include/linux/watch_queue.h
create mode 100644 kernel/watch_queue.c
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 4ef86433bd67..dbdc1ccbe949 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -202,6 +202,7 @@ Code Seq# Include File Comments
'W' 00-1F linux/wanrouter.h conflict! (pre 3.9)
'W' 00-3F sound/asound.h conflict!
'W' 40-5F drivers/pci/switch/switchtec.c
+'W' 60-61 linux/watch_queue.h
'X' all fs/xfs/xfs_fs.h, conflict!
fs/xfs/linux-2.6/xfs_ioctl32.h,
include/linux/falloc.h,
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
new file mode 100644
index 000000000000..d8f70282d247
--- /dev/null
+++ b/Documentation/watch_queue.rst
@@ -0,0 +1,354 @@
+==============================
+General notification mechanism
+==============================
+
+The general notification mechanism is built on top of the standard pipe driver
+whereby it effectively splices notification messages from the kernel into pipes
+opened by userspace. This can be used in conjunction with::
+
+ * Key/keyring notifications
+
+ * General device event notifications
+
+
+The notifications buffers can be enabled by:
+
+ "General setup"/"General notification queue"
+ (CONFIG_WATCH_QUEUE)
+
+This document has the following sections:
+
+.. contents:: :local:
+
+
+Overview
+========
+
+This facility appears as a pipe that is opened in a special mode. The pipe's
+internal ring buffer is used to hold messages that are generated by the kernel.
+These messages are then read out by read(). Splice and similar are disabled on
+such pipes due to them wanting to, under some circumstances, revert their
+additions to the ring - which might end up interleaved with notification
+messages.
+
+The owner of the pipe has to tell the kernel which sources it would like to
+watch through that pipe. Only sources that have been connected to a pipe will
+insert messages into it. Note that a source may be bound to multiple pipes and
+insert messages into all of them simultaneously.
+
+Filters may also be emplaced on a pipe so that certain source types and
+subevents can be ignored if they're not of interest.
+
+A message will be discarded if there isn't a slot available in the ring or if
+no preallocated message buffer is available. In both of these cases, read()
+will insert a WATCH_META_LOSS_NOTIFICATION message into the output buffer after
+the last message currently in the buffer has been read.
+
+Note that when producing a notification, the kernel does not wait for the
+consumers to collect it, but rather just continues on. This means that
+notifications can be generated whilst spinlocks are held and also protects the
+kernel from being held up indefinitely by a userspace malfunction.
+
+
+Message Structure
+=================
+
+Notification messages begin with a short header::
+
+ struct watch_notification {
+ __u32 type:24;
+ __u32 subtype:8;
+ __u32 info;
+ };
+
+"type" indicates the source of the notification record and "subtype" indicates
+the type of record from that source (see the Watch Sources section below). The
+type may also be "WATCH_TYPE_META". This is a special record type generated
+internally by the watch queue itself. There are two subtypes:
+
+ * WATCH_META_REMOVAL_NOTIFICATION
+ * WATCH_META_LOSS_NOTIFICATION
+
+The first indicates that an object on which a watch was installed was removed
+or destroyed and the second indicates that some messages have been lost.
+
+"info" indicates a bunch of things, including:
+
+ * The length of the message in bytes, including the header (mask with
+ WATCH_INFO_LENGTH and shift by WATCH_INFO_LENGTH__SHIFT). This indicates
+ the size of the record, which may be between 8 and 127 bytes.
+
+ * The watch ID (mask with WATCH_INFO_ID and shift by WATCH_INFO_ID__SHIFT).
+ This indicates that caller's ID of the watch, which may be between 0
+ and 255. Multiple watches may share a queue, and this provides a means to
+ distinguish them.
+
+ * A type-specific field (WATCH_INFO_TYPE_INFO). This is set by the
+ notification producer to indicate some meaning specific to the type and
+ subtype.
+
+Everything in info apart from the length can be used for filtering.
+
+The header can be followed by supplementary information. The format of this is
+at the discretion is defined by the type and subtype.
+
+
+Watch List (Notification Source) API
+====================================
+
+A "watch list" is a list of watchers that are subscribed to a source of
+notifications. A list may be attached to an object (say a key or a superblock)
+or may be global (say for device events). From a userspace perspective, a
+non-global watch list is typically referred to by reference to the object it
+belongs to (such as using KEYCTL_NOTIFY and giving it a key serial number to
+watch that specific key).
+
+To manage a watch list, the following functions are provided:
+
+ * ``void init_watch_list(struct watch_list *wlist,
+ void (*release_watch)(struct watch *wlist));``
+
+ Initialise a watch list. If ``release_watch`` is not NULL, then this
+ indicates a function that should be called when the watch_list object is
+ destroyed to discard any references the watch list holds on the watched
+ object.
+
+ * ``void remove_watch_list(struct watch_list *wlist);``
+
+ This removes all of the watches subscribed to a watch_list and frees them
+ and then destroys the watch_list object itself.
+
+
+Watch Queue (Notification Output) API
+=====================================
+
+A "watch queue" is the buffer allocated by an application that notification
+records will be written into. The workings of this are hidden entirely inside
+of the watch_queue device driver, but it is necessary to gain a reference to it
+to set a watch. These can be managed with:
+
+ * ``struct watch_queue *get_watch_queue(int fd);``
+
+ Since watch queues are indicated to the kernel by the fd of the pipe that
+ implements the buffer, userspace must hand that fd through a system call.
+ This can be used to look up an opaque pointer to the watch queue from the
+ system call.
+
+ * ``void put_watch_queue(struct watch_queue *wqueue);``
+
+ This discards the reference obtained from ``get_watch_queue()``.
+
+
+Watch Subscription API
+======================
+
+A "watch" is a subscription on a watch list, indicating the watch queue, and
+thus the buffer, into which notification records should be written. The watch
+queue object may also carry filtering rules for that object, as set by
+userspace. Some parts of the watch struct can be set by the driver::
+
+ struct watch {
+ union {
+ u32 info_id; /* ID to be OR'd in to info field */
+ ...
+ };
+ void *private; /* Private data for the watched object */
+ u64 id; /* Internal identifier */
+ ...
+ };
+
+The ``info_id`` value should be an 8-bit number obtained from userspace and
+shifted by WATCH_INFO_ID__SHIFT. This is OR'd into the WATCH_INFO_ID field of
+struct watch_notification::info when and if the notification is written into
+the associated watch queue buffer.
+
+The ``private`` field is the driver's data associated with the watch_list and
+is cleaned up by the ``watch_list::release_watch()`` method.
+
+The ``id`` field is the source's ID. Notifications that are posted with a
+different ID are ignored.
+
+The following functions are provided to manage watches:
+
+ * ``void init_watch(struct watch *watch, struct watch_queue *wqueue);``
+
+ Initialise a watch object, setting its pointer to the watch queue, using
+ appropriate barriering to avoid lockdep complaints.
+
+ * ``int add_watch_to_object(struct watch *watch, struct watch_list *wlist);``
+
+ Subscribe a watch to a watch list (notification source). The
+ driver-settable fields in the watch struct must have been set before this
+ is called.
+
+ * ``int remove_watch_from_object(struct watch_list *wlist,
+ struct watch_queue *wqueue,
+ u64 id, false);``
+
+ Remove a watch from a watch list, where the watch must match the specified
+ watch queue (``wqueue``) and object identifier (``id``). A notification
+ (``WATCH_META_REMOVAL_NOTIFICATION``) is sent to the watch queue to
+ indicate that the watch got removed.
+
+ * ``int remove_watch_from_object(struct watch_list *wlist, NULL, 0, true);``
+
+ Remove all the watches from a watch list. It is expected that this will be
+ called preparatory to destruction and that the watch list will be
+ inaccessible to new watches by this point. A notification
+ (``WATCH_META_REMOVAL_NOTIFICATION``) is sent to the watch queue of each
+ subscribed watch to indicate that the watch got removed.
+
+
+Notification Posting API
+========================
+
+To post a notification to watch list so that the subscribed watches can see it,
+the following function should be used::
+
+ void post_watch_notification(struct watch_list *wlist,
+ struct watch_notification *n,
+ const struct cred *cred,
+ u64 id);
+
+The notification should be preformatted and a pointer to the header (``n``)
+should be passed in. The notification may be larger than this and the size in
+units of buffer slots is noted in ``n->info & WATCH_INFO_LENGTH``.
+
+The ``cred`` struct indicates the credentials of the source (subject) and is
+passed to the LSMs, such as SELinux, to allow or suppress the recording of the
+note in each individual queue according to the credentials of that queue
+(object).
+
+The ``id`` is the ID of the source object (such as the serial number on a key).
+Only watches that have the same ID set in them will see this notification.
+
+
+Watch Sources
+=============
+
+Any particular buffer can be fed from multiple sources. Sources include:
+
+ * WATCH_TYPE_KEY_NOTIFY
+
+ Notifications of this type indicate changes to keys and keyrings, including
+ the changes of keyring contents or the attributes of keys.
+
+ See Documentation/security/keys/core.rst for more information.
+
+ * WATCH_TYPE_BLOCK_NOTIFY
+
+ Notifications of this type indicate block layer events, such as I/O errors
+ or temporary link loss. Watches of this type are set on a global queue.
+
+
+Event Filtering
+===============
+
+Once a watch queue has been created, a set of filters can be applied to limit
+the events that are received using::
+
+ struct watch_notification_filter filter = {
+ ...
+ };
+ ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter)
+
+The filter description is a variable of type::
+
+ struct watch_notification_filter {
+ __u32 nr_filters;
+ __u32 __reserved;
+ struct watch_notification_type_filter filters[];
+ };
+
+Where "nr_filters" is the number of filters in filters[] and "__reserved"
+should be 0. The "filters" array has elements of the following type::
+
+ struct watch_notification_type_filter {
+ __u32 type;
+ __u32 info_filter;
+ __u32 info_mask;
+ __u32 subtype_filter[8];
+ };
+
+Where:
+
+ * ``type`` is the event type to filter for and should be something like
+ "WATCH_TYPE_KEY_NOTIFY"
+
+ * ``info_filter`` and ``info_mask`` act as a filter on the info field of the
+ notification record. The notification is only written into the buffer if::
+
+ (watch.info & info_mask) == info_filter
+
+ This could be used, for example, to ignore events that are not exactly on
+ the watched point in a mount tree.
+
+ * ``subtype_filter`` is a bitmask indicating the subtypes that are of
+ interest. Bit 0 of subtype_filter[0] corresponds to subtype 0, bit 1 to
+ subtype 1, and so on.
+
+If the argument to the ioctl() is NULL, then the filters will be removed and
+all events from the watched sources will come through.
+
+
+Userspace Code Example
+======================
+
+A buffer is created with something like the following::
+
+ pipe2(fds, O_TMPFILE);
+ ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
+
+It can then be set to receive keyring change notifications and device event
+notifications::
+
+ keyctl(KEYCTL_WATCH_KEY, KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
+ watch_devices(fds[1], 0x2);
+
+The notifications can then be consumed by something like the following::
+
+ static void consumer(int rfd, struct watch_queue_buffer *buf)
+ {
+ unsigned char buffer[128];
+ ssize_t buf_len;
+
+ while (buf_len = read(rfd, buffer, sizeof(buffer)),
+ buf_len > 0
+ ) {
+ void *p = buffer;
+ void *end = buffer + buf_len;
+ while (p < end) {
+ union {
+ struct watch_notification n;
+ unsigned char buf1[128];
+ } n;
+ size_t largest, len;
+
+ largest = end - p;
+ if (largest > 128)
+ largest = 128;
+ memcpy(&n, p, largest);
+
+ len = (n->info & WATCH_INFO_LENGTH) >>
+ WATCH_INFO_LENGTH__SHIFT;
+ if (len == 0 || len > largest)
+ return;
+
+ switch (n.n.type) {
+ case WATCH_TYPE_META:
+ got_meta(&n.n);
+ case WATCH_TYPE_KEY_NOTIFY:
+ saw_key_change(&n.n);
+ break;
+ case WATCH_TYPE_BLOCK_NOTIFY:
+ saw_block_event(&n.n);
+ break;
+ case WATCH_TYPE_USB_NOTIFY:
+ saw_usb_event(&n.n);
+ break;
+ }
+
+ p += len;
+ }
+ }
+ }
diff --git a/fs/pipe.c b/fs/pipe.c
index 57502c3c0fba..5352c07be47f 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -24,6 +24,7 @@
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <linux/memcontrol.h>
+#include <linux/watch_queue.h>
#include <linux/uaccess.h>
#include <asm/ioctls.h>
@@ -450,6 +451,13 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
goto out;
}
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue) {
+ ret = -EXDEV;
+ goto out;
+ }
+#endif
+
/*
* Only wake up if the pipe started out empty, since
* otherwise there should be no readers waiting.
@@ -614,22 +622,37 @@ static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
int count, head, tail, mask;
switch (cmd) {
- case FIONREAD:
- __pipe_lock(pipe);
- count = 0;
- head = pipe->head;
- tail = pipe->tail;
- mask = pipe->ring_size - 1;
+ case FIONREAD:
+ __pipe_lock(pipe);
+ count = 0;
+ head = pipe->head;
+ tail = pipe->tail;
+ mask = pipe->ring_size - 1;
- while (tail != head) {
- count += pipe->bufs[tail & mask].len;
- tail++;
- }
- __pipe_unlock(pipe);
+ while (tail != head) {
+ count += pipe->bufs[tail & mask].len;
+ tail++;
+ }
+ __pipe_unlock(pipe);
- return put_user(count, (int __user *)arg);
- default:
- return -ENOIOCTLCMD;
+ return put_user(count, (int __user *)arg);
+
+#ifdef CONFIG_WATCH_QUEUE
+ case IOC_WATCH_QUEUE_SET_SIZE: {
+ int ret;
+ __pipe_lock(pipe);
+ ret = watch_queue_set_size(pipe, arg);
+ __pipe_unlock(pipe);
+ return ret;
+ }
+
+ case IOC_WATCH_QUEUE_SET_FILTER:
+ return watch_queue_set_filter(
+ pipe, (struct watch_notification_filter __user *)arg);
+#endif
+
+ default:
+ return -ENOIOCTLCMD;
}
}
@@ -735,27 +758,27 @@ pipe_fasync(int fd, struct file *filp, int on)
return retval;
}
-static unsigned long account_pipe_buffers(struct user_struct *user,
- unsigned long old, unsigned long new)
+unsigned long account_pipe_buffers(struct user_struct *user,
+ unsigned long old, unsigned long new)
{
return atomic_long_add_return(new - old, &user->pipe_bufs);
}
-static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
+bool too_many_pipe_buffers_soft(unsigned long user_bufs)
{
unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
return soft_limit && user_bufs > soft_limit;
}
-static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
+bool too_many_pipe_buffers_hard(unsigned long user_bufs)
{
unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
return hard_limit && user_bufs > hard_limit;
}
-static bool is_unprivileged_user(void)
+bool pipe_is_unprivileged_user(void)
{
return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
}
@@ -777,12 +800,12 @@ struct pipe_inode_info *alloc_pipe_info(void)
user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
- if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
+ if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) {
user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
pipe_bufs = 1;
}
- if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
+ if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
goto out_revert_acct;
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
@@ -793,6 +816,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
pipe->r_counter = pipe->w_counter = 1;
pipe->max_usage = pipe_bufs;
pipe->ring_size = pipe_bufs;
+ pipe->nr_accounted = pipe_bufs;
pipe->user = user;
mutex_init(&pipe->mutex);
return pipe;
@@ -810,7 +834,14 @@ void free_pipe_info(struct pipe_inode_info *pipe)
{
int i;
- (void) account_pipe_buffers(pipe->user, pipe->ring_size, 0);
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue) {
+ watch_queue_clear(pipe->watch_queue);
+ put_watch_queue(pipe->watch_queue);
+ }
+#endif
+
+ (void) account_pipe_buffers(pipe->user, pipe->nr_accounted, 0);
free_uid(pipe->user);
for (i = 0; i < pipe->ring_size; i++) {
struct pipe_buffer *buf = pipe->bufs + i;
@@ -886,6 +917,17 @@ int create_pipe_files(struct file **res, int flags)
if (!inode)
return -ENFILE;
+ if (flags & O_NOTIFICATION_PIPE) {
+#ifdef CONFIG_WATCH_QUEUE
+ if (watch_queue_init(inode->i_pipe) < 0) {
+ iput(inode);
+ return -ENOMEM;
+ }
+#else
+ return -ENOPKG;
+#endif
+ }
+
f = alloc_file_pseudo(inode, pipe_mnt, "",
O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
&pipefifo_fops);
@@ -916,7 +958,7 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags)
int error;
int fdw, fdr;
- if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
+ if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_NOTIFICATION_PIPE))
return -EINVAL;
error = create_pipe_files(files, flags);
@@ -1163,42 +1205,12 @@ unsigned int round_pipe_size(unsigned long size)
}
/*
- * Allocate a new array of pipe buffers and copy the info over. Returns the
- * pipe size if successful, or return -ERROR on error.
+ * Resize the pipe ring to a number of slots.
*/
-static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
{
struct pipe_buffer *bufs;
- unsigned int size, nr_slots, head, tail, mask, n;
- unsigned long user_bufs;
- long ret = 0;
-
- size = round_pipe_size(arg);
- nr_slots = size >> PAGE_SHIFT;
-
- if (!nr_slots)
- return -EINVAL;
-
- /*
- * If trying to increase the pipe capacity, check that an
- * unprivileged user is not trying to exceed various limits
- * (soft limit check here, hard limit check just below).
- * Decreasing the pipe capacity is always permitted, even
- * if the user is currently over a limit.
- */
- if (nr_slots > pipe->ring_size &&
- size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
- return -EPERM;
-
- user_bufs = account_pipe_buffers(pipe->user, pipe->ring_size, nr_slots);
-
- if (nr_slots > pipe->ring_size &&
- (too_many_pipe_buffers_hard(user_bufs) ||
- too_many_pipe_buffers_soft(user_bufs)) &&
- is_unprivileged_user()) {
- ret = -EPERM;
- goto out_revert_acct;
- }
+ unsigned int head, tail, mask, n;
/*
* We can shrink the pipe, if arg is greater than the ring occupancy.
@@ -1210,17 +1222,13 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
head = pipe->head;
tail = pipe->tail;
n = pipe_occupancy(pipe->head, pipe->tail);
- if (nr_slots < n) {
- ret = -EBUSY;
- goto out_revert_acct;
- }
+ if (nr_slots < n)
+ return -EBUSY;
bufs = kcalloc(nr_slots, sizeof(*bufs),
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
- if (unlikely(!bufs)) {
- ret = -ENOMEM;
- goto out_revert_acct;
- }
+ if (unlikely(!bufs))
+ return -ENOMEM;
/*
* The pipe array wraps around, so just start the new one at zero
@@ -1248,14 +1256,66 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
kfree(pipe->bufs);
pipe->bufs = bufs;
pipe->ring_size = nr_slots;
- pipe->max_usage = nr_slots;
+ if (pipe->max_usage > nr_slots)
+ pipe->max_usage = nr_slots;
pipe->tail = tail;
pipe->head = head;
wake_up_interruptible_all(&pipe->wait);
+ return 0;
+}
+
+/*
+ * Allocate a new array of pipe buffers and copy the info over. Returns the
+ * pipe size if successful, or return -ERROR on error.
+ */
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+{
+ unsigned long user_bufs;
+ unsigned int nr_slots, size;
+ long ret = 0;
+
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ return -EBUSY;
+#endif
+
+ size = round_pipe_size(arg);
+ nr_slots = size >> PAGE_SHIFT;
+
+ if (!nr_slots)
+ return -EINVAL;
+
+ /*
+ * If trying to increase the pipe capacity, check that an
+ * unprivileged user is not trying to exceed various limits
+ * (soft limit check here, hard limit check just below).
+ * Decreasing the pipe capacity is always permitted, even
+ * if the user is currently over a limit.
+ */
+ if (nr_slots > pipe->max_usage &&
+ size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
+ return -EPERM;
+
+ user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_slots);
+
+ if (nr_slots > pipe->max_usage &&
+ (too_many_pipe_buffers_hard(user_bufs) ||
+ too_many_pipe_buffers_soft(user_bufs)) &&
+ pipe_is_unprivileged_user()) {
+ ret = -EPERM;
+ goto out_revert_acct;
+ }
+
+ ret = pipe_resize_ring(pipe, nr_slots);
+ if (ret < 0)
+ goto out_revert_acct;
+
+ pipe->max_usage = nr_slots;
+ pipe->nr_accounted = nr_slots;
return pipe->max_usage * PAGE_SIZE;
out_revert_acct:
- (void) account_pipe_buffers(pipe->user, nr_slots, pipe->ring_size);
+ (void) account_pipe_buffers(pipe->user, nr_slots, pipe->nr_accounted);
return ret;
}
@@ -1264,9 +1324,17 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
* location, so checking ->i_pipe is not enough to verify that this is a
* pipe.
*/
-struct pipe_inode_info *get_pipe_info(struct file *file)
+struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice)
{
- return file->f_op == &pipefifo_fops ? file->private_data : NULL;
+ struct pipe_inode_info *pipe = file->private_data;
+
+ if (file->f_op != &pipefifo_fops || !pipe)
+ return NULL;
+#ifdef CONFIG_WATCH_QUEUE
+ if (for_splice && pipe->watch_queue)
+ return NULL;
+#endif
+ return pipe;
}
long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -1274,7 +1342,7 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
struct pipe_inode_info *pipe;
long ret;
- pipe = get_pipe_info(file);
+ pipe = get_pipe_info(file, false);
if (!pipe)
return -EBADF;
diff --git a/fs/splice.c b/fs/splice.c
index 3009652a41c8..44a999d30f3f 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1118,8 +1118,8 @@ static long do_splice(struct file *in, loff_t __user *off_in,
loff_t offset;
long ret;
- ipipe = get_pipe_info(in);
- opipe = get_pipe_info(out);
+ ipipe = get_pipe_info(in, true);
+ opipe = get_pipe_info(out, true);
if (ipipe && opipe) {
if (off_in || off_out)
@@ -1278,7 +1278,7 @@ static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
unsigned int flags)
{
- struct pipe_inode_info *pipe = get_pipe_info(file);
+ struct pipe_inode_info *pipe = get_pipe_info(file, true);
struct splice_desc sd = {
.total_len = iov_iter_count(iter),
.flags = flags,
@@ -1313,7 +1313,7 @@ static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
if (flags & SPLICE_F_GIFT)
buf_flag = PIPE_BUF_FLAG_GIFT;
- pipe = get_pipe_info(file);
+ pipe = get_pipe_info(file, true);
if (!pipe)
return -EBADF;
@@ -1766,8 +1766,8 @@ static int link_pipe(struct pipe_inode_info *ipipe,
static long do_tee(struct file *in, struct file *out, size_t len,
unsigned int flags)
{
- struct pipe_inode_info *ipipe = get_pipe_info(in);
- struct pipe_inode_info *opipe = get_pipe_info(out);
+ struct pipe_inode_info *ipipe = get_pipe_info(in, true);
+ struct pipe_inode_info *opipe = get_pipe_info(out, true);
int ret = -EINVAL;
/*
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index dbcfa6892384..cef70acd99bf 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -34,6 +34,7 @@ struct pipe_buffer {
* @tail: The point of buffer consumption
* @max_usage: The maximum number of slots that may be used in the ring
* @ring_size: total number of buffers (should be a power of 2)
+ * @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
* @tmp_page: cached released page
* @readers: number of current readers of this pipe
* @writers: number of current writers of this pipe
@@ -44,6 +45,7 @@ struct pipe_buffer {
* @fasync_writers: writer side fasync
* @bufs: the circular array of pipe buffers
* @user: the user who created this pipe
+ * @watch_queue: If this pipe is a watch_queue, this is the stuff for that
**/
struct pipe_inode_info {
struct mutex mutex;
@@ -52,6 +54,7 @@ struct pipe_inode_info {
unsigned int tail;
unsigned int max_usage;
unsigned int ring_size;
+ unsigned int nr_accounted;
unsigned int readers;
unsigned int writers;
unsigned int files;
@@ -62,6 +65,9 @@ struct pipe_inode_info {
struct fasync_struct *fasync_writers;
struct pipe_buffer *bufs;
struct user_struct *user;
+#ifdef CONFIG_WATCH_QUEUE
+ struct watch_queue *watch_queue;
+#endif
};
/*
@@ -236,9 +242,20 @@ void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
+#ifdef CONFIG_WATCH_QUEUE
+unsigned long account_pipe_buffers(struct user_struct *user,
+ unsigned long old, unsigned long new);
+bool too_many_pipe_buffers_soft(unsigned long user_bufs);
+bool too_many_pipe_buffers_hard(unsigned long user_bufs);
+bool pipe_is_unprivileged_user(void);
+#endif
+
/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
+#ifdef CONFIG_WATCH_QUEUE
+int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
+#endif
long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
-struct pipe_inode_info *get_pipe_info(struct file *file);
+struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
int create_pipe_files(struct file **, int);
unsigned int round_pipe_size(unsigned long size);
diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
new file mode 100644
index 000000000000..5e08db2adc31
--- /dev/null
+++ b/include/linux/watch_queue.h
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/* User-mappable watch queue
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([email protected])
+ *
+ * See Documentation/watch_queue.rst
+ */
+
+#ifndef _LINUX_WATCH_QUEUE_H
+#define _LINUX_WATCH_QUEUE_H
+
+#include <uapi/linux/watch_queue.h>
+#include <linux/kref.h>
+#include <linux/rcupdate.h>
+
+#ifdef CONFIG_WATCH_QUEUE
+
+struct cred;
+
+struct watch_type_filter {
+ enum watch_notification_type type;
+ __u32 subtype_filter[1]; /* Bitmask of subtypes to filter on */
+ __u32 info_filter; /* Filter on watch_notification::info */
+ __u32 info_mask; /* Mask of relevant bits in info_filter */
+};
+
+struct watch_filter {
+ union {
+ struct rcu_head rcu;
+ unsigned long type_filter[2]; /* Bitmask of accepted types */
+ };
+ u32 nr_filters; /* Number of filters */
+ struct watch_type_filter filters[];
+};
+
+struct watch_queue {
+ struct rcu_head rcu;
+ struct watch_filter __rcu *filter;
+ struct pipe_inode_info *pipe; /* The pipe we're using as a buffer */
+ struct hlist_head watches; /* Contributory watches */
+ struct page **notes; /* Preallocated notifications */
+ unsigned long *notes_bitmap; /* Allocation bitmap for notes */
+ struct kref usage; /* Object usage count */
+ spinlock_t lock;
+ unsigned int nr_notes; /* Number of notes */
+ unsigned int nr_pages; /* Number of pages in notes[] */
+ bool defunct; /* T when queues closed */
+};
+
+/*
+ * Representation of a watch on an object.
+ */
+struct watch {
+ union {
+ struct rcu_head rcu;
+ u32 info_id; /* ID to be OR'd in to info field */
+ };
+ struct watch_queue __rcu *queue; /* Queue to post events to */
+ struct hlist_node queue_node; /* Link in queue->watches */
+ struct watch_list __rcu *watch_list;
+ struct hlist_node list_node; /* Link in watch_list->watchers */
+ const struct cred *cred; /* Creds of the owner of the watch */
+ void *private; /* Private data for the watched object */
+ u64 id; /* Internal identifier */
+ struct kref usage; /* Object usage count */
+};
+
+/*
+ * List of watches on an object.
+ */
+struct watch_list {
+ struct rcu_head rcu;
+ struct hlist_head watchers;
+ void (*release_watch)(struct watch *);
+ spinlock_t lock;
+};
+
+extern void __post_watch_notification(struct watch_list *,
+ struct watch_notification *,
+ const struct cred *,
+ u64);
+extern struct watch_queue *get_watch_queue(int);
+extern void put_watch_queue(struct watch_queue *);
+extern void init_watch(struct watch *, struct watch_queue *);
+extern int add_watch_to_object(struct watch *, struct watch_list *);
+extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
+extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int);
+extern long watch_queue_set_filter(struct pipe_inode_info *,
+ struct watch_notification_filter __user *);
+extern int watch_queue_init(struct pipe_inode_info *);
+extern void watch_queue_clear(struct watch_queue *);
+
+static inline void init_watch_list(struct watch_list *wlist,
+ void (*release_watch)(struct watch *))
+{
+ INIT_HLIST_HEAD(&wlist->watchers);
+ spin_lock_init(&wlist->lock);
+ wlist->release_watch = release_watch;
+}
+
+static inline void post_watch_notification(struct watch_list *wlist,
+ struct watch_notification *n,
+ const struct cred *cred,
+ u64 id)
+{
+ if (unlikely(wlist))
+ __post_watch_notification(wlist, n, cred, id);
+}
+
+static inline void remove_watch_list(struct watch_list *wlist, u64 id)
+{
+ if (wlist) {
+ remove_watch_from_object(wlist, NULL, id, true);
+ kfree_rcu(wlist, rcu);
+ }
+}
+
+/**
+ * watch_sizeof - Calculate the information part of the size of a watch record,
+ * given the structure size.
+ */
+#define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)
+
+#endif
+
+#endif /* _LINUX_WATCH_QUEUE_H */
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 9df72227f515..3a5790f1f05d 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -4,9 +4,13 @@
#include <linux/types.h>
#include <linux/fcntl.h>
+#include <linux/ioctl.h>
#define O_NOTIFICATION_PIPE O_EXCL /* Parameter to pipe2() selecting notification pipe */
+#define IOC_WATCH_QUEUE_SET_SIZE _IO('W', 0x60) /* Set the size in pages */
+#define IOC_WATCH_QUEUE_SET_FILTER _IO('W', 0x61) /* Set the filter */
+
enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
WATCH_TYPE__NR = 1
@@ -41,6 +45,22 @@ struct watch_notification {
#define WATCH_INFO_FLAG_7 0x00800000
};
+/*
+ * Notification filtering rules (IOC_WATCH_QUEUE_SET_FILTER).
+ */
+struct watch_notification_type_filter {
+ __u32 type; /* Type to apply filter to */
+ __u32 info_filter; /* Filter on watch_notification::info */
+ __u32 info_mask; /* Mask of relevant bits in info_filter */
+ __u32 subtype_filter[8]; /* Bitmask of subtypes to filter on */
+};
+
+struct watch_notification_filter {
+ __u32 nr_filters; /* Number of filters */
+ __u32 __reserved; /* Must be 0 */
+ struct watch_notification_type_filter filters[];
+};
+
/*
* Extended watch removal notification. This is used optionally if the type
diff --git a/init/Kconfig b/init/Kconfig
index a34064a031a5..53cdcc25c920 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -338,6 +338,18 @@ config POSIX_MQUEUE_SYSCTL
depends on SYSCTL
default y
+config WATCH_QUEUE
+ bool "General notification queue"
+ default n
+ help
+
+ This is a general notification queue for the kernel to pass events to
+ userspace by splicing them into pipes. It can be used in conjunction
+ with watches for key/keyring change notifications and device
+ notifications.
+
+ See Documentation/watch_queue.rst
+
config CROSS_MEMORY_ATTACH
bool "Enable process_vm_readv/writev syscalls"
depends on MMU
diff --git a/kernel/Makefile b/kernel/Makefile
index f2cc0d118a0b..06d5255784b4 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
obj-$(CONFIG_HAS_IOMEM) += iomem.o
obj-$(CONFIG_RSEQ) += rseq.o
+obj-$(CONFIG_WATCH_QUEUE) += watch_queue.o
obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
new file mode 100644
index 000000000000..e2e3344a2586
--- /dev/null
+++ b/kernel/watch_queue.c
@@ -0,0 +1,657 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Watch queue and general notification mechanism, built on pipes
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([email protected])
+ *
+ * See Documentation/watch_queue.rst
+ */
+
+#define pr_fmt(fmt) "watchq: " fmt
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/printk.h>
+#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/poll.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/file.h>
+#include <linux/security.h>
+#include <linux/cred.h>
+#include <linux/sched/signal.h>
+#include <linux/watch_queue.h>
+#include <linux/pipe_fs_i.h>
+
+MODULE_DESCRIPTION("Watch queue");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+#define WATCH_QUEUE_NOTE_SIZE 128
+#define WATCH_QUEUE_NOTES_PER_PAGE (PAGE_SIZE / WATCH_QUEUE_NOTE_SIZE)
+
+static void watch_queue_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct watch_queue *wqueue = (struct watch_queue *)buf->private;
+ struct page *page;
+ unsigned int bit;
+
+ /* We need to work out which note within the page this refers to, but
+ * the note might have been maximum size, so merely ANDing the offset
+ * off doesn't work. OTOH, the note must've been more than zero size.
+ */
+ bit = buf->offset + buf->len;
+ if ((bit & (WATCH_QUEUE_NOTE_SIZE - 1)) == 0)
+ bit -= WATCH_QUEUE_NOTE_SIZE;
+ bit /= WATCH_QUEUE_NOTE_SIZE;
+
+ page = buf->page;
+ bit += page->index;
+
+ set_bit(bit, wqueue->notes_bitmap);
+}
+
+static int watch_queue_pipe_buf_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return -1; /* No. */
+}
+
+/* New data written to a pipe may be appended to a buffer with this type. */
+static const struct pipe_buf_operations watch_queue_pipe_buf_ops = {
+ .confirm = generic_pipe_buf_confirm,
+ .release = watch_queue_pipe_buf_release,
+ .steal = watch_queue_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
+/*
+ * Post a notification to a watch queue.
+ */
+static bool post_one_notification(struct watch_queue *wqueue,
+ struct watch_notification *n)
+{
+ void *p;
+ struct pipe_inode_info *pipe = wqueue->pipe;
+ struct pipe_buffer *buf;
+ struct page *page;
+ unsigned int head, tail, mask, note, offset, len;
+ bool done = false;
+
+ if (!pipe)
+ return false;
+
+ spin_lock_irq(&pipe->wait.lock);
+
+ if (wqueue->defunct)
+ goto out;
+
+ mask = pipe->ring_size - 1;
+ head = pipe->head;
+ tail = pipe->tail;
+ if (pipe_full(head, tail, pipe->ring_size))
+ goto lost;
+
+ note = find_first_bit(wqueue->notes_bitmap, wqueue->nr_notes);
+ if (note >= wqueue->nr_notes)
+ goto lost;
+
+ page = wqueue->notes[note / WATCH_QUEUE_NOTES_PER_PAGE];
+ offset = note % WATCH_QUEUE_NOTES_PER_PAGE * WATCH_QUEUE_NOTE_SIZE;
+ get_page(page);
+ len = n->info & WATCH_INFO_LENGTH;
+ p = kmap_atomic(page);
+ memcpy(p + offset, n, len);
+ kunmap_atomic(p);
+
+ buf = &pipe->bufs[head & mask];
+ buf->page = page;
+ buf->private = (unsigned long)wqueue;
+ buf->ops = &watch_queue_pipe_buf_ops;
+ buf->offset = offset;
+ buf->len = len;
+ buf->flags = 0;
+ pipe->head = head + 1;
+
+ if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
+ spin_unlock_irq(&pipe->wait.lock);
+ BUG();
+ }
+ wake_up_interruptible_sync_poll_locked(&pipe->wait, EPOLLIN | EPOLLRDNORM);
+ done = true;
+
+out:
+ spin_unlock_irq(&pipe->wait.lock);
+ if (done)
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ return done;
+
+lost:
+ goto out;
+}
+
+/*
+ * Apply filter rules to a notification.
+ */
+static bool filter_watch_notification(const struct watch_filter *wf,
+ const struct watch_notification *n)
+{
+ const struct watch_type_filter *wt;
+ unsigned int st_bits = sizeof(wt->subtype_filter[0]) * 8;
+ unsigned int st_index = n->subtype / st_bits;
+ unsigned int st_bit = 1U << (n->subtype % st_bits);
+ int i;
+
+ if (!test_bit(n->type, wf->type_filter))
+ return false;
+
+ for (i = 0; i < wf->nr_filters; i++) {
+ wt = &wf->filters[i];
+ if (n->type == wt->type &&
+ (wt->subtype_filter[st_index] & st_bit) &&
+ (n->info & wt->info_mask) == wt->info_filter)
+ return true;
+ }
+
+ return false; /* If there is a filter, the default is to reject. */
+}
+
+/**
+ * __post_watch_notification - Post an event notification
+ * @wlist: The watch list to post the event to.
+ * @n: The notification record to post.
+ * @cred: The creds of the process that triggered the notification.
+ * @id: The ID to match on the watch.
+ *
+ * Post a notification of an event into a set of watch queues and let the users
+ * know.
+ *
+ * The size of the notification should be set in n->info & WATCH_INFO_LENGTH and
+ * should be in units of sizeof(*n).
+ */
+void __post_watch_notification(struct watch_list *wlist,
+ struct watch_notification *n,
+ const struct cred *cred,
+ u64 id)
+{
+ const struct watch_filter *wf;
+ struct watch_queue *wqueue;
+ struct watch *watch;
+
+ if (((n->info & WATCH_INFO_LENGTH) >> WATCH_INFO_LENGTH__SHIFT) == 0) {
+ WARN_ON(1);
+ return;
+ }
+
+ rcu_read_lock();
+
+ hlist_for_each_entry_rcu(watch, &wlist->watchers, list_node) {
+ if (watch->id != id)
+ continue;
+ n->info &= ~WATCH_INFO_ID;
+ n->info |= watch->info_id;
+
+ wqueue = rcu_dereference(watch->queue);
+ wf = rcu_dereference(wqueue->filter);
+ if (wf && !filter_watch_notification(wf, n))
+ continue;
+
+ if (security_post_notification(watch->cred, cred, n) < 0)
+ continue;
+
+ post_one_notification(wqueue, n);
+ }
+
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(__post_watch_notification);
+
+/*
+ * Allocate sufficient pages to preallocation for the requested number of
+ * notifications.
+ */
+long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
+{
+ struct watch_queue *wqueue = pipe->watch_queue;
+ struct page **pages;
+ unsigned long *bitmap;
+ unsigned long user_bufs;
+ unsigned int bmsize;
+ int ret, i, nr_pages;
+
+ if (!wqueue)
+ return -ENODEV;
+ if (wqueue->notes)
+ return -EBUSY;
+
+ if (nr_notes < 1 ||
+ nr_notes > 512) /* TODO: choose a better hard limit */
+ return -EINVAL;
+
+ nr_pages = (nr_notes + WATCH_QUEUE_NOTES_PER_PAGE - 1);
+ nr_pages /= WATCH_QUEUE_NOTES_PER_PAGE;
+ user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_pages);
+
+ if (nr_pages > pipe->max_usage &&
+ (too_many_pipe_buffers_hard(user_bufs) ||
+ too_many_pipe_buffers_soft(user_bufs)) &&
+ pipe_is_unprivileged_user()) {
+ ret = -EPERM;
+ goto error;
+ }
+
+ ret = pipe_resize_ring(pipe, nr_notes);
+ if (ret < 0)
+ goto error;
+
+ pages = kcalloc(sizeof(struct page *), nr_pages, GFP_KERNEL);
+ if (!pages)
+ goto error;
+
+ for (i = 0; i < nr_pages; i++) {
+ pages[i] = alloc_page(GFP_KERNEL);
+ if (!pages[i])
+ goto error_p;
+ pages[i]->index = i * WATCH_QUEUE_NOTES_PER_PAGE;
+ }
+
+ bmsize = (nr_notes + BITS_PER_LONG - 1) / BITS_PER_LONG;
+ bmsize *= sizeof(unsigned long);
+ bitmap = kmalloc(bmsize, GFP_KERNEL);
+ if (!bitmap)
+ goto error_p;
+
+ memset(bitmap, 0xff, bmsize);
+ wqueue->notes = pages;
+ wqueue->notes_bitmap = bitmap;
+ wqueue->nr_pages = nr_pages;
+ wqueue->nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
+ return 0;
+
+error_p:
+ for (i = 0; i < nr_pages; i++)
+ __free_page(pages[i]);
+ kfree(pages);
+error:
+ (void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
+ return ret;
+}
+
+/*
+ * Set the filter on a watch queue.
+ */
+long watch_queue_set_filter(struct pipe_inode_info *pipe,
+ struct watch_notification_filter __user *_filter)
+{
+ struct watch_notification_type_filter *tf;
+ struct watch_notification_filter filter;
+ struct watch_type_filter *q;
+ struct watch_filter *wfilter;
+ struct watch_queue *wqueue = pipe->watch_queue;
+ int ret, nr_filter = 0, i;
+
+ if (!wqueue)
+ return -ENODEV;
+
+ if (!_filter) {
+ /* Remove the old filter */
+ wfilter = NULL;
+ goto set;
+ }
+
+ /* Grab the user's filter specification */
+ if (copy_from_user(&filter, _filter, sizeof(filter)) != 0)
+ return -EFAULT;
+ if (filter.nr_filters == 0 ||
+ filter.nr_filters > 16 ||
+ filter.__reserved != 0)
+ return -EINVAL;
+
+ tf = memdup_user(_filter->filters, filter.nr_filters * sizeof(*tf));
+ if (IS_ERR(tf))
+ return PTR_ERR(tf);
+
+ ret = -EINVAL;
+ for (i = 0; i < filter.nr_filters; i++) {
+ if ((tf[i].info_filter & ~tf[i].info_mask) ||
+ tf[i].info_mask & WATCH_INFO_LENGTH)
+ goto err_filter;
+ /* Ignore any unknown types */
+ if (tf[i].type >= sizeof(wfilter->type_filter) * 8)
+ continue;
+ nr_filter++;
+ }
+
+ /* Now we need to build the internal filter from only the relevant
+ * user-specified filters.
+ */
+ ret = -ENOMEM;
+ wfilter = kzalloc(struct_size(wfilter, filters, nr_filter), GFP_KERNEL);
+ if (!wfilter)
+ goto err_filter;
+ wfilter->nr_filters = nr_filter;
+
+ q = wfilter->filters;
+ for (i = 0; i < filter.nr_filters; i++) {
+ if (tf[i].type >= sizeof(wfilter->type_filter) * BITS_PER_LONG)
+ continue;
+
+ q->type = tf[i].type;
+ q->info_filter = tf[i].info_filter;
+ q->info_mask = tf[i].info_mask;
+ q->subtype_filter[0] = tf[i].subtype_filter[0];
+ __set_bit(q->type, wfilter->type_filter);
+ q++;
+ }
+
+ kfree(tf);
+set:
+ pipe_lock(pipe);
+ rcu_swap_protected(wqueue->filter, wfilter,
+ lockdep_is_held(&pipe->mutex));
+ pipe_unlock(pipe);
+ if (wfilter)
+ kfree_rcu(wfilter, rcu);
+ return 0;
+
+err_filter:
+ kfree(tf);
+ return ret;
+}
+
+static void __put_watch_queue(struct kref *kref)
+{
+ struct watch_queue *wqueue =
+ container_of(kref, struct watch_queue, usage);
+ struct watch_filter *wfilter;
+ int i;
+
+ for (i = 0; i < wqueue->nr_pages; i++)
+ __free_page(wqueue->notes[i]);
+
+ wfilter = rcu_access_pointer(wqueue->filter);
+ if (wfilter)
+ kfree_rcu(wfilter, rcu);
+ kfree_rcu(wqueue, rcu);
+}
+
+/**
+ * put_watch_queue - Dispose of a ref on a watchqueue.
+ * @wqueue: The watch queue to unref.
+ */
+void put_watch_queue(struct watch_queue *wqueue)
+{
+ kref_put(&wqueue->usage, __put_watch_queue);
+}
+EXPORT_SYMBOL(put_watch_queue);
+
+static void free_watch(struct rcu_head *rcu)
+{
+ struct watch *watch = container_of(rcu, struct watch, rcu);
+
+ put_watch_queue(rcu_access_pointer(watch->queue));
+ put_cred(watch->cred);
+}
+
+static void __put_watch(struct kref *kref)
+{
+ struct watch *watch = container_of(kref, struct watch, usage);
+
+ call_rcu(&watch->rcu, free_watch);
+}
+
+/*
+ * Discard a watch.
+ */
+static void put_watch(struct watch *watch)
+{
+ kref_put(&watch->usage, __put_watch);
+}
+
+/**
+ * init_watch_queue - Initialise a watch
+ * @watch: The watch to initialise.
+ * @wqueue: The queue to assign.
+ *
+ * Initialise a watch and set the watch queue.
+ */
+void init_watch(struct watch *watch, struct watch_queue *wqueue)
+{
+ kref_init(&watch->usage);
+ INIT_HLIST_NODE(&watch->list_node);
+ INIT_HLIST_NODE(&watch->queue_node);
+ rcu_assign_pointer(watch->queue, wqueue);
+}
+
+/**
+ * add_watch_to_object - Add a watch on an object to a watch list
+ * @watch: The watch to add
+ * @wlist: The watch list to add to
+ *
+ * @watch->queue must have been set to point to the queue to post notifications
+ * to and the watch list of the object to be watched. @watch->cred must also
+ * have been set to the appropriate credentials and a ref taken on them.
+ *
+ * The caller must pin the queue and the list both and must hold the list
+ * locked against racing watch additions/removals.
+ */
+int add_watch_to_object(struct watch *watch, struct watch_list *wlist)
+{
+ struct watch_queue *wqueue = rcu_access_pointer(watch->queue);
+ struct watch *w;
+
+ hlist_for_each_entry(w, &wlist->watchers, list_node) {
+ struct watch_queue *wq = rcu_access_pointer(w->queue);
+ if (wqueue == wq && watch->id == w->id)
+ return -EBUSY;
+ }
+
+ watch->cred = get_current_cred();
+ rcu_assign_pointer(watch->watch_list, wlist);
+
+ spin_lock_bh(&wqueue->lock);
+ kref_get(&wqueue->usage);
+ kref_get(&watch->usage);
+ hlist_add_head(&watch->queue_node, &wqueue->watches);
+ spin_unlock_bh(&wqueue->lock);
+
+ hlist_add_head(&watch->list_node, &wlist->watchers);
+ return 0;
+}
+EXPORT_SYMBOL(add_watch_to_object);
+
+/**
+ * remove_watch_from_object - Remove a watch or all watches from an object.
+ * @wlist: The watch list to remove from
+ * @wq: The watch queue of interest (ignored if @all is true)
+ * @id: The ID of the watch to remove (ignored if @all is true)
+ * @all: True to remove all objects
+ *
+ * Remove a specific watch or all watches from an object. A notification is
+ * sent to the watcher to tell them that this happened.
+ */
+int remove_watch_from_object(struct watch_list *wlist, struct watch_queue *wq,
+ u64 id, bool all)
+{
+ struct watch_notification_removal n;
+ struct watch_queue *wqueue;
+ struct watch *watch;
+ int ret = -EBADSLT;
+
+ rcu_read_lock();
+
+again:
+ spin_lock(&wlist->lock);
+ hlist_for_each_entry(watch, &wlist->watchers, list_node) {
+ if (all ||
+ (watch->id == id && rcu_access_pointer(watch->queue) == wq))
+ goto found;
+ }
+ spin_unlock(&wlist->lock);
+ goto out;
+
+found:
+ ret = 0;
+ hlist_del_init_rcu(&watch->list_node);
+ rcu_assign_pointer(watch->watch_list, NULL);
+ spin_unlock(&wlist->lock);
+
+ /* We now own the reference on watch that used to belong to wlist. */
+
+ n.watch.type = WATCH_TYPE_META;
+ n.watch.subtype = WATCH_META_REMOVAL_NOTIFICATION;
+ n.watch.info = watch->info_id | watch_sizeof(n.watch);
+ n.id = id;
+ if (id != 0)
+ n.watch.info = watch->info_id | watch_sizeof(n);
+
+ wqueue = rcu_dereference(watch->queue);
+
+ /* We don't need the watch list lock for the next bit as RCU is
+ * protecting *wqueue from deallocation.
+ */
+ if (wqueue) {
+ post_one_notification(wqueue, &n.watch);
+
+ spin_lock_bh(&wqueue->lock);
+
+ if (!hlist_unhashed(&watch->queue_node)) {
+ hlist_del_init_rcu(&watch->queue_node);
+ put_watch(watch);
+ }
+
+ spin_unlock_bh(&wqueue->lock);
+ }
+
+ if (wlist->release_watch) {
+ void (*release_watch)(struct watch *);
+
+ release_watch = wlist->release_watch;
+ rcu_read_unlock();
+ (*release_watch)(watch);
+ rcu_read_lock();
+ }
+ put_watch(watch);
+
+ if (all && !hlist_empty(&wlist->watchers))
+ goto again;
+out:
+ rcu_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(remove_watch_from_object);
+
+/*
+ * Remove all the watches that are contributory to a queue. This has the
+ * potential to race with removal of the watches by the destruction of the
+ * objects being watched or with the distribution of notifications.
+ */
+void watch_queue_clear(struct watch_queue *wqueue)
+{
+ struct watch_list *wlist;
+ struct watch *watch;
+ bool release;
+
+ rcu_read_lock();
+ spin_lock_bh(&wqueue->lock);
+
+ /* Prevent new additions and prevent notifications from happening */
+ wqueue->defunct = true;
+
+ while (!hlist_empty(&wqueue->watches)) {
+ watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);
+ hlist_del_init_rcu(&watch->queue_node);
+ /* We now own a ref on the watch. */
+ spin_unlock_bh(&wqueue->lock);
+
+ /* We can't do the next bit under the queue lock as we need to
+ * get the list lock - which would cause a deadlock if someone
+ * was removing from the opposite direction at the same time or
+ * posting a notification.
+ */
+ wlist = rcu_dereference(watch->watch_list);
+ if (wlist) {
+ void (*release_watch)(struct watch *);
+
+ spin_lock(&wlist->lock);
+
+ release = !hlist_unhashed(&watch->list_node);
+ if (release) {
+ hlist_del_init_rcu(&watch->list_node);
+ rcu_assign_pointer(watch->watch_list, NULL);
+
+ /* We now own a second ref on the watch. */
+ }
+
+ release_watch = wlist->release_watch;
+ spin_unlock(&wlist->lock);
+
+ if (release) {
+ if (release_watch) {
+ rcu_read_unlock();
+ /* This might need to call dput(), so
+ * we have to drop all the locks.
+ */
+ (*release_watch)(watch);
+ rcu_read_lock();
+ }
+ put_watch(watch);
+ }
+ }
+
+ put_watch(watch);
+ spin_lock_bh(&wqueue->lock);
+ }
+
+ spin_unlock_bh(&wqueue->lock);
+ rcu_read_unlock();
+}
+
+/**
+ * get_watch_queue - Get a watch queue from its file descriptor.
+ * @fd: The fd to query.
+ */
+struct watch_queue *get_watch_queue(int fd)
+{
+ struct pipe_inode_info *pipe;
+ struct watch_queue *wqueue = ERR_PTR(-EINVAL);
+ struct fd f;
+
+ f = fdget(fd);
+ if (f.file) {
+ pipe = get_pipe_info(f.file, false);
+ if (pipe && pipe->watch_queue) {
+ wqueue = pipe->watch_queue;
+ kref_get(&wqueue->usage);
+ }
+ fdput(f);
+ }
+
+ return wqueue;
+}
+EXPORT_SYMBOL(get_watch_queue);
+
+/*
+ * Initialise a watch queue
+ */
+int watch_queue_init(struct pipe_inode_info *pipe)
+{
+ struct watch_queue *wqueue;
+
+ wqueue = kzalloc(sizeof(*wqueue), GFP_KERNEL);
+ if (!wqueue)
+ return -ENOMEM;
+
+ wqueue->pipe = pipe;
+ kref_init(&wqueue->usage);
+ spin_lock_init(&wqueue->lock);
+ INIT_HLIST_HEAD(&wqueue->watches);
+
+ pipe->watch_queue = wqueue;
+ return 0;
+}
The sample program is run like:
./samples/watch_queue/watch_test
and watches "/" for mount changes and the current session keyring for key
changes:
# keyctl add user a a @s
1035096409
# keyctl unlink 1035096409 @s
producing:
# ./watch_test
read() = 16
NOTIFY[000]: ty=000001 sy=02 i=00000110
KEY 2ffc2e5d change=2[linked] aux=1035096409
read() = 16
NOTIFY[000]: ty=000001 sy=02 i=00000110
KEY 2ffc2e5d change=3[unlinked] aux=1035096409
Other events may be produced, such as with a failing disk:
read() = 22
NOTIFY[000]: ty=000003 sy=02 i=00000416
USB 3-7.7 dev-reset e=0 r=0
read() = 24
NOTIFY[000]: ty=000002 sy=06 i=00000418
BLOCK 00800050 e=6[critical medium] s=64000ef8
This corresponds to:
blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
in dmesg.
Signed-off-by: David Howells <[email protected]>
---
samples/Kconfig | 6 +
samples/Makefile | 1
samples/watch_queue/Makefile | 7 +
samples/watch_queue/watch_test.c | 183 ++++++++++++++++++++++++++++++++++++++
4 files changed, 197 insertions(+)
create mode 100644 samples/watch_queue/Makefile
create mode 100644 samples/watch_queue/watch_test.c
diff --git a/samples/Kconfig b/samples/Kconfig
index 9d236c346de5..5c31971a5745 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -190,5 +190,11 @@ config SAMPLE_INTEL_MEI
help
Build a sample program to work with mei device.
+config SAMPLE_WATCH_QUEUE
+ bool "Build example /dev/watch_queue notification consumer"
+ depends on HEADERS_INSTALL
+ help
+ Build example userspace program to use the new mount_notify(),
+ sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 5ce50ef0f2b2..a80ab2dbaae7 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_VIDEO_PCI_SKELETON) += v4l/
obj-y += vfio-mdev/
subdir-$(CONFIG_SAMPLE_VFS) += vfs
obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/
+subdir-$(CONFIG_SAMPLE_WATCH_QUEUE) += watch_queue
diff --git a/samples/watch_queue/Makefile b/samples/watch_queue/Makefile
new file mode 100644
index 000000000000..eec00dd0a8df
--- /dev/null
+++ b/samples/watch_queue/Makefile
@@ -0,0 +1,7 @@
+# List of programs to build
+hostprogs-y := watch_test
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_watch_test.o += -I$(objtree)/usr/include
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
new file mode 100644
index 000000000000..9bf60abf5c7e
--- /dev/null
+++ b/samples/watch_queue/watch_test.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Use /dev/watch_queue to watch for notifications.
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([email protected])
+ */
+
+#define _GNU_SOURCE
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <limits.h>
+#include <linux/watch_queue.h>
+#include <linux/unistd.h>
+#include <linux/keyctl.h>
+
+#ifndef KEYCTL_WATCH_KEY
+#define KEYCTL_WATCH_KEY -1
+#endif
+#ifndef __NR_watch_devices
+#define __NR_watch_devices -1
+#endif
+
+#define BUF_SIZE 256
+
+static long keyctl_watch_key(int key, int watch_fd, int watch_id)
+{
+ return syscall(__NR_keyctl, KEYCTL_WATCH_KEY, key, watch_fd, watch_id);
+}
+
+static const char *key_subtypes[256] = {
+ [NOTIFY_KEY_INSTANTIATED] = "instantiated",
+ [NOTIFY_KEY_UPDATED] = "updated",
+ [NOTIFY_KEY_LINKED] = "linked",
+ [NOTIFY_KEY_UNLINKED] = "unlinked",
+ [NOTIFY_KEY_CLEARED] = "cleared",
+ [NOTIFY_KEY_REVOKED] = "revoked",
+ [NOTIFY_KEY_INVALIDATED] = "invalidated",
+ [NOTIFY_KEY_SETATTR] = "setattr",
+};
+
+static void saw_key_change(struct watch_notification *n, size_t len)
+{
+ struct key_notification *k = (struct key_notification *)n;
+
+ if (len != sizeof(struct key_notification)) {
+ fprintf(stderr, "Incorrect key message length\n");
+ return;
+ }
+
+ printf("KEY %08x change=%u[%s] aux=%u\n",
+ k->key_id, n->subtype, key_subtypes[n->subtype], k->aux);
+}
+
+/*
+ * Consume and display events.
+ */
+static void consumer(int fd)
+{
+ unsigned char buffer[4096], *p, *end;
+ union {
+ struct watch_notification n;
+ unsigned char buf1[128];
+ } n;
+ ssize_t buf_len;
+
+ for (;;) {
+ buf_len = read(fd, buffer, sizeof(buffer));
+ if (buf_len == -1) {
+ perror("read");
+ exit(1);
+ }
+
+ if (buf_len == 0) {
+ printf("-- END --\n");
+ return;
+ }
+
+ if (buf_len > sizeof(buffer)) {
+ fprintf(stderr, "Read buffer overrun: %zd\n", buf_len);
+ return;
+ }
+
+ printf("read() = %zd\n", buf_len);
+
+ p = buffer;
+ end = buffer + buf_len;
+ while (p < end) {
+ size_t largest, len;
+
+ largest = end - p;
+ if (largest > 128)
+ largest = 128;
+ if (largest < sizeof(struct watch_notification)) {
+ fprintf(stderr, "Short message header: %zu\n", largest);
+ return;
+ }
+ memcpy(&n, p, largest);
+
+ printf("NOTIFY[%03zx]: ty=%06x sy=%02x i=%08x\n",
+ p - buffer, n.n.type, n.n.subtype, n.n.info);
+
+ len = n.n.info & WATCH_INFO_LENGTH;
+ if (len < sizeof(n.n) || len > largest) {
+ fprintf(stderr, "Bad message length: %zu/%zu\n", len, largest);
+ exit(1);
+ }
+
+ switch (n.n.type) {
+ case WATCH_TYPE_META:
+ switch (n.n.subtype) {
+ case WATCH_META_REMOVAL_NOTIFICATION:
+ printf("REMOVAL of watchpoint %08x\n",
+ (n.n.info & WATCH_INFO_ID) >>
+ WATCH_INFO_ID__SHIFT);
+ break;
+ default:
+ printf("other meta record\n");
+ break;
+ }
+ break;
+ case WATCH_TYPE_KEY_NOTIFY:
+ saw_key_change(&n.n, len);
+ break;
+ default:
+ printf("other type\n");
+ break;
+ }
+
+ p += len;
+ }
+ }
+}
+
+static struct watch_notification_filter filter = {
+ .nr_filters = 1,
+ .filters = {
+ [0] = {
+ .type = WATCH_TYPE_KEY_NOTIFY,
+ .subtype_filter[0] = UINT_MAX,
+ },
+ },
+};
+
+int main(int argc, char **argv)
+{
+ int pipefd[2], fd;
+
+ if (pipe2(pipefd, O_NOTIFICATION_PIPE) == -1) {
+ perror("pipe2");
+ exit(1);
+ }
+ fd = pipefd[0];
+
+ if (ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, BUF_SIZE) == -1) {
+ perror("/dev/watch_queue(size)");
+ exit(1);
+ }
+
+ if (ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter) == -1) {
+ perror("/dev/watch_queue(filter)");
+ exit(1);
+ }
+
+ if (keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fd, 0x01) == -1) {
+ perror("keyctl");
+ exit(1);
+ }
+
+ if (keyctl_watch_key(KEY_SPEC_USER_KEYRING, fd, 0x02) == -1) {
+ perror("keyctl");
+ exit(1);
+ }
+
+ consumer(fd);
+ exit(0);
+}
Create a general, global watch list that can be used for the posting of
device notification events, for such things as device attachment,
detachment and errors on sources such as block devices and USB devices.
This can be enabled with:
CONFIG_DEVICE_NOTIFICATIONS
To add a watch on this list, an event queue must be created and configured:
pipe2(fds, O_NOTIFICATION_PIPE);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
and then a watch can be placed upon it using a system call:
watch_devices(fds[1], 12, 0);
Unless the application wants to receive all events, it should employ
appropriate filters. For example, to receive just USB notifications, it
could do:
struct watch_notification_filter filter = {
.nr_filters = 1,
.filters = {
[0] = {
.type = WATCH_TYPE_USB_NOTIFY,
.subtype_filter[0] = UINT_MAX;
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
Signed-off-by: David Howells <[email protected]>
---
Documentation/watch_queue.rst | 22 ++++++-
arch/alpha/kernel/syscalls/syscall.tbl | 1
arch/arm/tools/syscall.tbl | 1
arch/arm64/include/asm/unistd.h | 2 -
arch/arm64/include/asm/unistd32.h | 2 +
arch/ia64/kernel/syscalls/syscall.tbl | 1
arch/m68k/kernel/syscalls/syscall.tbl | 1
arch/microblaze/kernel/syscalls/syscall.tbl | 1
arch/mips/kernel/syscalls/syscall_n32.tbl | 1
arch/mips/kernel/syscalls/syscall_n64.tbl | 1
arch/mips/kernel/syscalls/syscall_o32.tbl | 1
arch/parisc/kernel/syscalls/syscall.tbl | 1
arch/powerpc/kernel/syscalls/syscall.tbl | 1
arch/s390/kernel/syscalls/syscall.tbl | 1
arch/sh/kernel/syscalls/syscall.tbl | 1
arch/sparc/kernel/syscalls/syscall.tbl | 1
arch/x86/entry/syscalls/syscall_32.tbl | 1
arch/x86/entry/syscalls/syscall_64.tbl | 1
arch/xtensa/kernel/syscalls/syscall.tbl | 1
drivers/base/Kconfig | 9 +++
drivers/base/Makefile | 1
drivers/base/watch.c | 90 +++++++++++++++++++++++++++
include/linux/device.h | 7 ++
include/linux/syscalls.h | 1
include/uapi/asm-generic/unistd.h | 4 +
kernel/sys_ni.c | 1
26 files changed, 152 insertions(+), 3 deletions(-)
create mode 100644 drivers/base/watch.c
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index d8f70282d247..ed592700be0e 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -223,6 +223,25 @@ The ``id`` is the ID of the source object (such as the serial number on a key).
Only watches that have the same ID set in them will see this notification.
+Global Device Watch List
+========================
+
+There is a global watch list that hardware generated events, such as device
+connection, disconnection, failure and error can be posted upon. It must be
+enabled using::
+
+ CONFIG_DEVICE_NOTIFICATIONS
+
+Watchpoints are set in userspace using the device_notify(2) system call.
+Within the kernel events are posted upon it using::
+
+ void post_device_notification(struct watch_notification *n, u64 id);
+
+where ``n`` is the formatted notification record to post. ``id`` is an
+identifier that can be used to direct to specific watches, but it should be 0
+for general use on this queue.
+
+
Watch Sources
=============
@@ -238,7 +257,8 @@ Any particular buffer can be fed from multiple sources. Sources include:
* WATCH_TYPE_BLOCK_NOTIFY
Notifications of this type indicate block layer events, such as I/O errors
- or temporary link loss. Watches of this type are set on a global queue.
+ or temporary link loss. Watches of this type are set on the global device
+ watch list.
Event Filtering
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 8e13b0b2928d..3b355b0996a1 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -475,3 +475,4 @@
543 common fspick sys_fspick
544 common pidfd_open sys_pidfd_open
# 545 reserved for clone3
+546 common watch_devices sys_watch_devices
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 6da7dc4d79cc..0f080cf44cc9 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -449,3 +449,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 2629a68b8724..368761302768 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -38,7 +38,7 @@
#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
-#define __NR_compat_syscalls 436
+#define __NR_compat_syscalls 437
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 94ab29cf4f00..b5310789ce7a 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -879,6 +879,8 @@ __SYSCALL(__NR_fspick, sys_fspick)
__SYSCALL(__NR_pidfd_open, sys_pidfd_open)
#define __NR_clone3 435
__SYSCALL(__NR_clone3, sys_clone3)
+#define __NR_watch_devices 436
+__SYSCALL(__NR_watch_devices, sys_watch_devices)
/*
* Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index 36d5faf4c86c..2f33f5db2fed 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -356,3 +356,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index a88a285a0e5f..83e4e8784b88 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -435,3 +435,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 09b0cd7dab0a..9a70a3be3b7b 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -441,3 +441,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index e7c5ab38e403..b39527fc32c9 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -374,3 +374,4 @@
433 n32 fspick sys_fspick
434 n32 pidfd_open sys_pidfd_open
435 n32 clone3 __sys_clone3
+436 n32 watch_devices sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 13cd66581f3b..a7f0c5e71768 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -350,3 +350,4 @@
433 n64 fspick sys_fspick
434 n64 pidfd_open sys_pidfd_open
435 n64 clone3 __sys_clone3
+436 n64 watch_devices sys_watch_devices
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 353539ea4140..6f378288598c 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -423,3 +423,4 @@
433 o32 fspick sys_fspick
434 o32 pidfd_open sys_pidfd_open
435 o32 clone3 __sys_clone3
+436 o32 watch_devices sys_watch_devices
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 285ff516150c..b64bbafa5919 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -433,3 +433,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3_wrapper
+436 common watch_devices sys_watch_devices
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 43f736ed47f2..0a503239ab5c 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -517,3 +517,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 nospu clone3 ppc_clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 3054e9c035a3..19b43c0d928a 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -438,3 +438,4 @@
433 common fspick sys_fspick sys_fspick
434 common pidfd_open sys_pidfd_open sys_pidfd_open
435 common clone3 sys_clone3 sys_clone3
+436 common watch_devices sys_watch_devices sys_watch_devices
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index b5ed26c4c005..b454e07c9372 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -438,3 +438,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 8c8cc7537fb2..8ef43c27457e 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -481,3 +481,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
# 435 reserved for clone3
+436 common watch_devices sys_watch_devices
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 15908eb9b17e..bdf7e845d1f8 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -440,3 +440,4 @@
433 i386 fspick sys_fspick __ia32_sys_fspick
434 i386 pidfd_open sys_pidfd_open __ia32_sys_pidfd_open
435 i386 clone3 sys_clone3 __ia32_sys_clone3
+436 i386 watch_devices sys_watch_devices __ia32_sys_watch_devices
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index c29976eca4a8..29293d103829 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -357,6 +357,7 @@
433 common fspick __x64_sys_fspick
434 common pidfd_open __x64_sys_pidfd_open
435 common clone3 __x64_sys_clone3/ptregs
+436 common watch_devices __x64_sys_watch_devices
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 25f4de729a6d..243fa18b8d1e 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -406,3 +406,4 @@
433 common fspick sys_fspick
434 common pidfd_open sys_pidfd_open
435 common clone3 sys_clone3
+436 common watch_devices sys_watch_devices
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index c3b3b5c0b0da..d4ae1c1adf69 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -1,6 +1,15 @@
# SPDX-License-Identifier: GPL-2.0
menu "Generic Driver Options"
+config DEVICE_NOTIFICATIONS
+ bool "Provide device event notifications"
+ depends on WATCH_QUEUE
+ help
+ This option provides support for getting hardware event notifications
+ on devices, buses and interfaces. This makes use of the
+ /dev/watch_queue misc device to handle the notification buffer.
+ device_notify(2) is used to set/remove watches.
+
config UEVENT_HELPER
bool "Support for uevent helper"
help
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 157452080f3d..4db2e8f1a1f4 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -7,6 +7,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \
attribute_container.o transport_class.o \
topology.o container.o property.o cacheinfo.o \
devcon.o swnode.o
+obj-$(CONFIG_DEVICE_NOTIFICATIONS) += watch.o
obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-y += power/
obj-$(CONFIG_ISA_BUS_API) += isa.o
diff --git a/drivers/base/watch.c b/drivers/base/watch.c
new file mode 100644
index 000000000000..725aaa24275b
--- /dev/null
+++ b/drivers/base/watch.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Event notifications.
+ *
+ * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([email protected])
+ */
+
+#include <linux/device.h>
+#include <linux/watch_queue.h>
+#include <linux/syscalls.h>
+#include <linux/init_task.h>
+#include <linux/security.h>
+
+/*
+ * Global queue for watching for device layer events.
+ */
+static struct watch_list device_watchers = {
+ .watchers = HLIST_HEAD_INIT,
+ .lock = __SPIN_LOCK_UNLOCKED(&device_watchers.lock),
+};
+
+static DEFINE_SPINLOCK(device_watchers_lock);
+
+/**
+ * post_device_notification - Post notification of a device event
+ * @n - The notification to post
+ * @id - The device ID
+ *
+ * Note that there's only a global queue to which all events are posted. Might
+ * want to provide per-dev queues also.
+ */
+void post_device_notification(struct watch_notification *n, u64 id)
+{
+ post_watch_notification(&device_watchers, n, &init_cred, id);
+}
+EXPORT_SYMBOL(post_device_notification);
+
+/**
+ * sys_watch_devices - Watch for device events.
+ * @watch_fd: The watch queue to send notifications to.
+ * @watch_id: The watch ID to be placed in the notification (-1 to remove watch)
+ * @flags: Flags (reserved for future)
+ */
+SYSCALL_DEFINE3(watch_devices, int, watch_fd, int, watch_id, unsigned int, flags)
+{
+ struct watch_queue *wqueue;
+ struct watch *watch = NULL;
+ long ret = -ENOMEM;
+
+ if (watch_id < -1 || watch_id > 0xff || flags)
+ return -EINVAL;
+
+ wqueue = get_watch_queue(watch_fd);
+ if (IS_ERR(wqueue)) {
+ ret = PTR_ERR(wqueue);
+ goto err;
+ }
+
+ if (watch_id >= 0) {
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (!watch)
+ goto err_wqueue;
+
+ init_watch(watch, wqueue);
+ watch->info_id = (u32)watch_id << WATCH_INFO_ID__SHIFT;
+
+ ret = security_watch_devices();
+ if (ret < 0)
+ goto err_watch;
+
+ spin_lock(&device_watchers_lock);
+ ret = add_watch_to_object(watch, &device_watchers);
+ spin_unlock(&device_watchers_lock);
+ if (ret == 0)
+ watch = NULL;
+ } else {
+ spin_lock(&device_watchers_lock);
+ ret = remove_watch_from_object(&device_watchers, wqueue, 0,
+ false);
+ spin_unlock(&device_watchers_lock);
+ }
+
+err_watch:
+ kfree(watch);
+err_wqueue:
+ put_watch_queue(wqueue);
+err:
+ return ret;
+}
diff --git a/include/linux/device.h b/include/linux/device.h
index 96ff76731e93..f32de6466092 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -43,6 +43,7 @@ struct iommu_group;
struct iommu_fwspec;
struct dev_pin_info;
struct iommu_param;
+struct watch_notification;
struct bus_attribute {
struct attribute attr;
@@ -1687,6 +1688,12 @@ void device_link_remove(void *consumer, struct device *supplier);
void device_links_supplier_sync_state_pause(void);
void device_links_supplier_sync_state_resume(void);
+#ifdef CONFIG_DEVICE_NOTIFICATIONS
+extern void post_device_notification(struct watch_notification *n, u64 id);
+#else
+static inline void post_device_notification(struct watch_notification *n, u64 id) {}
+#endif
+
#ifndef dev_fmt
#define dev_fmt(fmt) fmt
#endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 2960dedcfde8..393661015a30 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1000,6 +1000,7 @@ asmlinkage long sys_fspick(int dfd, const char __user *path, unsigned int flags)
asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
siginfo_t __user *info,
unsigned int flags);
+asmlinkage long sys_watch_devices(int watch_fd, int watch_id, unsigned int flags);
/*
* Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 1fc8faa6e973..4794d3c2afd7 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -850,9 +850,11 @@ __SYSCALL(__NR_pidfd_open, sys_pidfd_open)
#define __NR_clone3 435
__SYSCALL(__NR_clone3, sys_clone3)
#endif
+#define __NR_watch_devices 436
+__SYSCALL(__NR_watch_devices, sys_watch_devices)
#undef __NR_syscalls
-#define __NR_syscalls 436
+#define __NR_syscalls 437
/*
* 32 bit systems traditionally used different
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 3b69a560a7ac..0e9b275260f8 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -51,6 +51,7 @@ COND_SYSCALL_COMPAT(io_pgetevents);
COND_SYSCALL(io_uring_setup);
COND_SYSCALL(io_uring_enter);
COND_SYSCALL(io_uring_register);
+COND_SYSCALL(watch_devices);
/* fs/xattr.c */
Add handling for loss of notifications by having read() insert a
loss-notification message after it has read the pipe buffer that was last
in the ring when the loss occurred.
Lossage can come about either by running out of notification descriptors or
by running out of space in the pipe ring.
Signed-off-by: David Howells <[email protected]>
---
fs/pipe.c | 28 ++++++++++++++++++++++++++++
include/linux/pipe_fs_i.h | 7 +++++++
kernel/watch_queue.c | 2 ++
samples/watch_queue/watch_test.c | 3 +++
4 files changed, 40 insertions(+)
diff --git a/fs/pipe.c b/fs/pipe.c
index 05d0b02ed08d..423aafca4338 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -311,6 +311,30 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
unsigned int tail = pipe->tail;
unsigned int mask = pipe->ring_size - 1;
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->note_loss) {
+ struct watch_notification n;
+
+ if (total_len < 8) {
+ if (ret == 0)
+ ret = -ENOBUFS;
+ break;
+ }
+
+ n.type = WATCH_TYPE_META;
+ n.subtype = WATCH_META_LOSS_NOTIFICATION;
+ n.info = watch_sizeof(n);
+ if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) {
+ if (ret == 0)
+ ret = -EFAULT;
+ break;
+ }
+ ret += sizeof(n);
+ total_len -= sizeof(n);
+ pipe->note_loss = false;
+ }
+#endif
+
if (!pipe_empty(head, tail)) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
size_t chars = buf->len;
@@ -352,6 +376,10 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (!buf->len) {
pipe_buf_release(pipe, buf);
spin_lock_irq(&pipe->wait.lock);
+#ifdef CONFIG_WATCH_QUEUE
+ if (buf->flags & PIPE_BUF_FLAG_LOSS)
+ pipe->note_loss = true;
+#endif
tail++;
pipe->tail = tail;
spin_unlock_irq(&pipe->wait.lock);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index f86ae087aaca..810eb2b1efc6 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -9,6 +9,9 @@
#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
#define PIPE_BUF_FLAG_WHOLE 0x10 /* read() must return entire buffer or error */
+#ifdef CONFIG_WATCH_QUEUE
+#define PIPE_BUF_FLAG_LOSS 0x20 /* Message loss happened after this buffer */
+#endif
/**
* struct pipe_buffer - a linux kernel pipe buffer
@@ -33,6 +36,7 @@ struct pipe_buffer {
* @wait: reader/writer wait point in case of empty/full pipe
* @head: The point of buffer production
* @tail: The point of buffer consumption
+ * @note_loss: The next read() should insert a data-lost message
* @max_usage: The maximum number of slots that may be used in the ring
* @ring_size: total number of buffers (should be a power of 2)
* @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
@@ -55,6 +59,9 @@ struct pipe_inode_info {
unsigned int tail;
unsigned int max_usage;
unsigned int ring_size;
+#ifdef CONFIG_WATCH_QUEUE
+ bool note_loss;
+#endif
unsigned int nr_accounted;
unsigned int readers;
unsigned int writers;
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index a01f2fed0983..d48f422f391a 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -132,6 +132,8 @@ static bool post_one_notification(struct watch_queue *wqueue,
return done;
lost:
+ buf = &pipe->bufs[(head - 1) & mask];
+ buf->flags |= PIPE_BUF_FLAG_LOSS;
goto out;
}
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 924e13a49c37..0eaff5dc04c3 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -120,6 +120,9 @@ static void consumer(int fd)
(n.n.info & WATCH_INFO_ID) >>
WATCH_INFO_ID__SHIFT);
break;
+ case WATCH_META_LOSS_NOTIFICATION:
+ printf("-- LOSS --\n");
+ break;
default:
printf("other meta record\n");
break;
Add a block layer notification mechanism whereby notifications about
block-layer events such as I/O errors, can be reported to a monitoring
process asynchronously.
Firstly, an event queue needs to be created:
pipe2(fds, O_NOTIFICATION_PIPE);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
then a notification can be set up to report block notifications via that
queue:
struct watch_notification_filter filter = {
.nr_filters = 1,
.filters = {
[0] = {
.type = WATCH_TYPE_BLOCK_NOTIFY,
.subtype_filter[0] = UINT_MAX;
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
watch_devices(fds[1], 12);
After that, records will be placed into the queue when, for example, errors
occur on a block device. Records are of the following format:
struct block_notification {
struct watch_notification watch;
__u64 dev;
__u64 sector;
} *n;
Where:
n->watch.type will be WATCH_TYPE_BLOCK_NOTIFY
n->watch.subtype will be the type of notification, such as
NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM.
n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
record.
n->watch.info & WATCH_INFO_ID will be the second argument to
watch_devices(), shifted.
n->dev will be the device numbers munged together.
n->sector will indicate the affected sector (if appropriate for the
event).
Note that it is permissible for event records to be of variable length -
or, at least, the length may be dependent on the subtype.
Signed-off-by: David Howells <[email protected]>
---
Documentation/watch_queue.rst | 4 +++-
block/Kconfig | 9 +++++++++
block/blk-core.c | 29 ++++++++++++++++++++++++++++
include/linux/blkdev.h | 15 ++++++++++++++
include/uapi/linux/watch_queue.h | 30 ++++++++++++++++++++++++++++-
samples/watch_queue/watch_test.c | 40 +++++++++++++++++++++++++++++++++++++-
6 files changed, 124 insertions(+), 3 deletions(-)
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index ed592700be0e..f2299f631ae8 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -8,7 +8,9 @@ opened by userspace. This can be used in conjunction with::
* Key/keyring notifications
- * General device event notifications
+ * General device event notifications, including::
+
+ * Block layer event notifications
The notifications buffers can be enabled by:
diff --git a/block/Kconfig b/block/Kconfig
index c23094a14a2b..9fa6ce2177bc 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -181,6 +181,15 @@ config BLK_SED_OPAL
Enabling this option enables users to setup/unlock/lock
Locking ranges for SED devices using the Opal protocol.
+config BLK_NOTIFICATIONS
+ bool "Block layer event notifications"
+ depends on DEVICE_NOTIFICATIONS
+ help
+ This option provides support for getting block layer event
+ notifications. This makes use of the /dev/watch_queue misc device to
+ handle the notification buffer and provides the device_notify() system
+ call to enable/disable watches.
+
menu "Partition Types"
source "block/partitions/Kconfig"
diff --git a/block/blk-core.c b/block/blk-core.c
index 089e890ab208..50a5de025d5e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -187,6 +187,22 @@ static const struct {
[BLK_STS_IOERR] = { -EIO, "I/O" },
};
+#ifdef CONFIG_BLK_NOTIFICATIONS
+static const
+enum block_notification_type blk_notifications[ARRAY_SIZE(blk_errors)] = {
+ [BLK_STS_TIMEOUT] = NOTIFY_BLOCK_ERROR_TIMEOUT,
+ [BLK_STS_NOSPC] = NOTIFY_BLOCK_ERROR_NO_SPACE,
+ [BLK_STS_TRANSPORT] = NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT,
+ [BLK_STS_TARGET] = NOTIFY_BLOCK_ERROR_CRITICAL_TARGET,
+ [BLK_STS_NEXUS] = NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS,
+ [BLK_STS_MEDIUM] = NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM,
+ [BLK_STS_PROTECTION] = NOTIFY_BLOCK_ERROR_PROTECTION,
+ [BLK_STS_RESOURCE] = NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE,
+ [BLK_STS_DEV_RESOURCE] = NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE,
+ [BLK_STS_IOERR] = NOTIFY_BLOCK_ERROR_IO,
+};
+#endif
+
blk_status_t errno_to_blk_status(int errno)
{
int i;
@@ -227,6 +243,19 @@ static void print_req_error(struct request *req, blk_status_t status,
req->cmd_flags & ~REQ_OP_MASK,
req->nr_phys_segments,
IOPRIO_PRIO_CLASS(req->ioprio));
+
+#ifdef CONFIG_BLK_NOTIFICATIONS
+ if (blk_notifications[idx]) {
+ struct block_notification n = {
+ .watch.type = WATCH_TYPE_BLOCK_NOTIFY,
+ .watch.subtype = blk_notifications[idx],
+ .watch.info = watch_sizeof(n),
+ .dev = req->rq_disk ? disk_devt(req->rq_disk) : 0,
+ .sector = blk_rq_pos(req),
+ };
+ post_block_notification(&n);
+ }
+#endif
}
static void req_bio_endio(struct request *rq, struct bio *bio,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 47eb22a3b7f9..3cd1853dbdac 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -27,6 +27,7 @@
#include <linux/percpu-refcount.h>
#include <linux/scatterlist.h>
#include <linux/blkzoned.h>
+#include <linux/watch_queue.h>
struct module;
struct scsi_ioctl_command;
@@ -1770,6 +1771,20 @@ static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
}
#endif /* CONFIG_BLK_DEV_ZONED */
+#ifdef CONFIG_BLK_NOTIFICATIONS
+static inline void post_block_notification(struct block_notification *n)
+{
+ u64 id = 0; /* Might want to allow dev# here. */
+
+ post_device_notification(&n->watch, id);
+}
+#else
+static inline void post_block_notification(struct block_notification *n)
+{
+}
+#endif
+
+
#else /* CONFIG_BLOCK */
struct block_device;
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index c3d8320b5d3a..557771413242 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -14,7 +14,8 @@
enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
WATCH_TYPE_KEY_NOTIFY = 1, /* Key change event notification */
- WATCH_TYPE__NR = 2
+ WATCH_TYPE_BLOCK_NOTIFY = 2, /* Block layer event notification */
+ WATCH_TYPE__NR = 3
};
enum watch_meta_notification_subtype {
@@ -101,4 +102,31 @@ struct key_notification {
__u32 aux; /* Per-type auxiliary data */
};
+/*
+ * Type of block layer notification.
+ */
+enum block_notification_type {
+ NOTIFY_BLOCK_ERROR_TIMEOUT = 1, /* Timeout error */
+ NOTIFY_BLOCK_ERROR_NO_SPACE = 2, /* Critical space allocation error */
+ NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT = 3, /* Recoverable transport error */
+ NOTIFY_BLOCK_ERROR_CRITICAL_TARGET = 4, /* Critical target error */
+ NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS = 5, /* Critical nexus error */
+ NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM = 6, /* Critical medium error */
+ NOTIFY_BLOCK_ERROR_PROTECTION = 7, /* Protection error */
+ NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE = 8, /* Kernel resource error */
+ NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE = 9, /* Device resource error */
+ NOTIFY_BLOCK_ERROR_IO = 10, /* Other I/O error */
+};
+
+/*
+ * Block layer notification record.
+ * - watch.type = WATCH_TYPE_BLOCK_NOTIFY
+ * - watch.subtype = enum block_notification_type
+ */
+struct block_notification {
+ struct watch_notification watch; /* WATCH_TYPE_BLOCK_NOTIFY */
+ __u64 dev; /* Device number */
+ __u64 sector; /* Affected sector */
+};
+
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 0eaff5dc04c3..f5260fb792d1 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -58,6 +58,32 @@ static void saw_key_change(struct watch_notification *n, size_t len)
k->key_id, n->subtype, key_subtypes[n->subtype], k->aux);
}
+static const char *block_subtypes[256] = {
+ [NOTIFY_BLOCK_ERROR_TIMEOUT] = "timeout",
+ [NOTIFY_BLOCK_ERROR_NO_SPACE] = "critical space allocation",
+ [NOTIFY_BLOCK_ERROR_RECOVERABLE_TRANSPORT] = "recoverable transport",
+ [NOTIFY_BLOCK_ERROR_CRITICAL_TARGET] = "critical target",
+ [NOTIFY_BLOCK_ERROR_CRITICAL_NEXUS] = "critical nexus",
+ [NOTIFY_BLOCK_ERROR_CRITICAL_MEDIUM] = "critical medium",
+ [NOTIFY_BLOCK_ERROR_PROTECTION] = "protection",
+ [NOTIFY_BLOCK_ERROR_KERNEL_RESOURCE] = "kernel resource",
+ [NOTIFY_BLOCK_ERROR_DEVICE_RESOURCE] = "device resource",
+ [NOTIFY_BLOCK_ERROR_IO] = "I/O",
+};
+
+static void saw_block_change(struct watch_notification *n, size_t len)
+{
+ struct block_notification *b = (struct block_notification *)n;
+
+ if (len < sizeof(struct block_notification))
+ return;
+
+ printf("BLOCK %08llx e=%u[%s] s=%llx\n",
+ (unsigned long long)b->dev,
+ n->subtype, block_subtypes[n->subtype],
+ (unsigned long long)b->sector);
+}
+
/*
* Consume and display events.
*/
@@ -131,6 +157,9 @@ static void consumer(int fd)
case WATCH_TYPE_KEY_NOTIFY:
saw_key_change(&n.n, len);
break;
+ case WATCH_TYPE_BLOCK_NOTIFY:
+ saw_block_change(&n.n, len);
+ break;
default:
printf("other type\n");
break;
@@ -142,12 +171,16 @@ static void consumer(int fd)
}
static struct watch_notification_filter filter = {
- .nr_filters = 1,
+ .nr_filters = 2,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
+ [1] = {
+ .type = WATCH_TYPE_BLOCK_NOTIFY,
+ .subtype_filter[0] = UINT_MAX,
+ },
},
};
@@ -181,6 +214,11 @@ int main(int argc, char **argv)
exit(1);
}
+ if (syscall(__NR_watch_devices, fd, 0x04, 0) == -1) {
+ perror("watch_devices");
+ exit(1);
+ }
+
consumer(fd);
exit(0);
}
Add a USB subsystem notification mechanism whereby notifications about
hardware events such as device connection, disconnection, reset and I/O
errors, can be reported to a monitoring process asynchronously.
Firstly, an event queue needs to be created:
pipe2(fds, O_NOTIFICATION_PIPE);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, 256);
then a notification can be set up to report USB notifications via that
queue:
struct watch_notification_filter filter = {
.nr_filters = 1,
.filters = {
[0] = {
.type = WATCH_TYPE_USB_NOTIFY,
.subtype_filter[0] = UINT_MAX;
},
},
};
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
notify_devices(fds[1], 12);
After that, messages will be placed into the queue when events occur on a
USB device or bus. Messages are of the following format:
struct usb_notification {
struct watch_notification watch;
__u32 error;
__u32 reserved;
__u8 name_len;
__u8 name[0];
} *n;
Where:
n->watch.type will be WATCH_TYPE_USB_NOTIFY
n->watch.subtype will be the type of notification, such as
NOTIFY_USB_DEVICE_ADD.
n->watch.info & WATCH_INFO_LENGTH will indicate the length of the
message.
n->watch.info & WATCH_INFO_ID will be the second argument to
device_notify(), shifted.
n->error and n->reserved are intended to convey information such as
error codes, but are currently not used
n->name_len and n->name convey the USB device name as an
unterminated string. This may be truncated - it is currently
limited to a maximum 63 chars.
Note that it is permissible for messages to be of variable length - or, at
least, the length may be dependent on the subtype.
Signed-off-by: David Howells <[email protected]>
cc: Greg Kroah-Hartman <[email protected]>
cc: [email protected]
---
Documentation/watch_queue.rst | 9 +++++++
drivers/usb/core/Kconfig | 9 +++++++
drivers/usb/core/devio.c | 47 ++++++++++++++++++++++++++++++++++++++
drivers/usb/core/hub.c | 4 +++
include/linux/usb.h | 18 +++++++++++++++
include/uapi/linux/watch_queue.h | 28 ++++++++++++++++++++++-
samples/watch_queue/watch_test.c | 29 +++++++++++++++++++++++
7 files changed, 142 insertions(+), 2 deletions(-)
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
index f2299f631ae8..5321a9cb1ab2 100644
--- a/Documentation/watch_queue.rst
+++ b/Documentation/watch_queue.rst
@@ -12,6 +12,8 @@ opened by userspace. This can be used in conjunction with::
* Block layer event notifications
+ * USB subsystem event notifications
+
The notifications buffers can be enabled by:
@@ -262,6 +264,13 @@ Any particular buffer can be fed from multiple sources. Sources include:
or temporary link loss. Watches of this type are set on the global device
watch list.
+ * WATCH_TYPE_USB_NOTIFY
+
+ Notifications of this type indicate USB subsystem events, such as
+ attachment, removal, reset and I/O errors. Separate events are generated
+ for buses and devices. Watchpoints of this type are set on the global
+ device watch list.
+
Event Filtering
===============
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index ecaacc8ed311..57e7b649e48b 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -102,3 +102,12 @@ config USB_AUTOSUSPEND_DELAY
The default value Linux has always had is 2 seconds. Change
this value if you want a different delay and cannot modify
the command line or module parameter.
+
+config USB_NOTIFICATIONS
+ bool "Provide USB hardware event notifications"
+ depends on USB && DEVICE_NOTIFICATIONS
+ help
+ This option provides support for getting hardware event notifications
+ on USB devices and interfaces. This makes use of the
+ /dev/watch_queue misc device to handle the notification buffer.
+ device_notify(2) is used to set/remove watches.
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 12bb5722b420..3436a2bb6e98 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -41,6 +41,7 @@
#include <linux/dma-mapping.h>
#include <asm/byteorder.h>
#include <linux/moduleparam.h>
+#include <linux/watch_queue.h>
#include "usb.h"
@@ -2747,13 +2748,59 @@ static void usbdev_remove(struct usb_device *udev)
mutex_unlock(&usbfs_mutex);
}
+#ifdef CONFIG_USB_NOTIFICATIONS
+static noinline void post_usb_notification(const char *devname,
+ enum usb_notification_type subtype,
+ u32 error)
+{
+ unsigned int name_len, n_len;
+ u64 id = 0; /* We can put a device ID here for separate dev watches */
+
+ struct {
+ struct usb_notification n;
+ char more_name[USB_NOTIFICATION_MAX_NAME_LEN -
+ (sizeof(struct usb_notification) -
+ offsetof(struct usb_notification, name))];
+ } n;
+
+ name_len = strlen(devname);
+ name_len = min_t(size_t, name_len, USB_NOTIFICATION_MAX_NAME_LEN);
+ n_len = offsetof(struct usb_notification, name) + name_len;
+
+ memset(&n, 0, sizeof(n));
+ memcpy(n.n.name, devname, n_len);
+
+ n.n.watch.type = WATCH_TYPE_USB_NOTIFY;
+ n.n.watch.subtype = subtype;
+ n.n.watch.info = n_len;
+ n.n.error = error;
+ n.n.name_len = name_len;
+
+ post_device_notification(&n.n.watch, id);
+}
+
+void post_usb_device_notification(const struct usb_device *udev,
+ enum usb_notification_type subtype, u32 error)
+{
+ post_usb_notification(dev_name(&udev->dev), subtype, error);
+}
+
+void post_usb_bus_notification(const struct usb_bus *ubus,
+ enum usb_notification_type subtype, u32 error)
+{
+ post_usb_notification(ubus->bus_name, subtype, error);
+}
+#endif
+
static int usbdev_notify(struct notifier_block *self,
unsigned long action, void *dev)
{
switch (action) {
case USB_DEVICE_ADD:
+ post_usb_device_notification(dev, NOTIFY_USB_DEVICE_ADD, 0);
break;
case USB_DEVICE_REMOVE:
+ post_usb_device_notification(dev, NOTIFY_USB_DEVICE_REMOVE, 0);
usbdev_remove(dev);
break;
}
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index f229ad6952c0..eaf28eed51b0 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -30,6 +30,7 @@
#include <linux/random.h>
#include <linux/pm_qos.h>
#include <linux/kobject.h>
+#include <linux/watch_queue.h>
#include <linux/uaccess.h>
#include <asm/byteorder.h>
@@ -4606,6 +4607,9 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
(udev->config) ? "reset" : "new", speed,
devnum, driver_name);
+ if (udev->config)
+ post_usb_device_notification(udev, NOTIFY_USB_DEVICE_RESET, 0);
+
/* Set up TT records, if needed */
if (hdev->tt) {
udev->tt = hdev->tt;
diff --git a/include/linux/usb.h b/include/linux/usb.h
index e656e7b4b1e4..93fa0666f95a 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -26,6 +26,7 @@
struct usb_device;
struct usb_driver;
struct wusb_dev;
+enum usb_notification_type;
/*-------------------------------------------------------------------------*/
@@ -2015,6 +2016,23 @@ extern void usb_led_activity(enum usb_led_event ev);
static inline void usb_led_activity(enum usb_led_event ev) {}
#endif
+/*
+ * Notification functions.
+ */
+#ifdef CONFIG_USB_NOTIFICATIONS
+extern void post_usb_device_notification(const struct usb_device *udev,
+ enum usb_notification_type subtype,
+ u32 error);
+extern void post_usb_bus_notification(const struct usb_bus *ubus,
+ enum usb_notification_type subtype,
+ u32 error);
+#else
+static inline void post_usb_device_notification(const struct usb_device *udev,
+ unsigned int subtype, u32 error) {}
+static inline void post_usb_bus_notification(const struct usb_bus *ubus,
+ unsigned int subtype, u32 error) {}
+#endif
+
#endif /* __KERNEL__ */
#endif
diff --git a/include/uapi/linux/watch_queue.h b/include/uapi/linux/watch_queue.h
index 557771413242..ad1ae229674a 100644
--- a/include/uapi/linux/watch_queue.h
+++ b/include/uapi/linux/watch_queue.h
@@ -15,7 +15,8 @@ enum watch_notification_type {
WATCH_TYPE_META = 0, /* Special record */
WATCH_TYPE_KEY_NOTIFY = 1, /* Key change event notification */
WATCH_TYPE_BLOCK_NOTIFY = 2, /* Block layer event notification */
- WATCH_TYPE__NR = 3
+ WATCH_TYPE_USB_NOTIFY = 3, /* USB subsystem event notification */
+ WATCH_TYPE__NR = 4
};
enum watch_meta_notification_subtype {
@@ -129,4 +130,29 @@ struct block_notification {
__u64 sector; /* Affected sector */
};
+/*
+ * Type of USB layer notification.
+ */
+enum usb_notification_type {
+ NOTIFY_USB_DEVICE_ADD = 0, /* USB device added */
+ NOTIFY_USB_DEVICE_REMOVE = 1, /* USB device removed */
+ NOTIFY_USB_DEVICE_RESET = 2, /* USB device reset */
+ NOTIFY_USB_DEVICE_ERROR = 3, /* USB device error */
+};
+
+/*
+ * USB subsystem notification record.
+ * - watch.type = WATCH_TYPE_USB_NOTIFY
+ * - watch.subtype = enum usb_notification_type
+ */
+struct usb_notification {
+ struct watch_notification watch; /* WATCH_TYPE_USB_NOTIFY */
+ __u32 error;
+ __u32 reserved;
+ __u8 name_len; /* Length of device name */
+ __u8 name[0]; /* Device name (padded to __u64, truncated at 63 chars) */
+};
+
+#define USB_NOTIFICATION_MAX_NAME_LEN 63
+
#endif /* _UAPI_LINUX_WATCH_QUEUE_H */
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index f5260fb792d1..e4d47dfcc5d7 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -84,6 +84,26 @@ static void saw_block_change(struct watch_notification *n, size_t len)
(unsigned long long)b->sector);
}
+static const char *usb_subtypes[256] = {
+ [NOTIFY_USB_DEVICE_ADD] = "dev-add",
+ [NOTIFY_USB_DEVICE_REMOVE] = "dev-remove",
+ [NOTIFY_USB_DEVICE_RESET] = "dev-reset",
+ [NOTIFY_USB_DEVICE_ERROR] = "dev-error",
+};
+
+static void saw_usb_event(struct watch_notification *n, size_t len)
+{
+ struct usb_notification *u = (struct usb_notification *)n;
+
+ if (len < sizeof(struct usb_notification))
+ return;
+
+ printf("USB %*.*s %s e=%x r=%x\n",
+ u->name_len, u->name_len, u->name,
+ usb_subtypes[n->subtype],
+ u->error, u->reserved);
+}
+
/*
* Consume and display events.
*/
@@ -160,6 +180,9 @@ static void consumer(int fd)
case WATCH_TYPE_BLOCK_NOTIFY:
saw_block_change(&n.n, len);
break;
+ case WATCH_TYPE_USB_NOTIFY:
+ saw_usb_event(&n.n, len);
+ break;
default:
printf("other type\n");
break;
@@ -171,7 +194,7 @@ static void consumer(int fd)
}
static struct watch_notification_filter filter = {
- .nr_filters = 2,
+ .nr_filters = 3,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
@@ -181,6 +204,10 @@ static struct watch_notification_filter filter = {
.type = WATCH_TYPE_BLOCK_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
+ [2] = {
+ .type = WATCH_TYPE_USB_NOTIFY,
+ .subtype_filter[0] = UINT_MAX,
+ },
},
};
Implement the watch_key security hook to make sure that a key grants the
caller View permission in order to set a watch on a key.
For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.
Signed-off-by: David Howells <[email protected]>
Acked-by: Stephen Smalley <[email protected]>
---
security/selinux/hooks.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 116b4d644f68..d838d1b58d88 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6587,6 +6587,17 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
*_buffer = context;
return rc;
}
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+static int selinux_watch_key(struct key *key)
+{
+ struct key_security_struct *ksec = key->security;
+ u32 sid = current_sid();
+
+ return avc_has_perm(&selinux_state,
+ sid, ksec->sid, SECCLASS_KEY, KEY_NEED_VIEW, NULL);
+}
+#endif
#endif
#ifdef CONFIG_SECURITY_INFINIBAND
@@ -7081,6 +7092,9 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(key_free, selinux_key_free),
LSM_HOOK_INIT(key_permission, selinux_key_permission),
LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ LSM_HOOK_INIT(watch_key, selinux_watch_key),
+#endif
#endif
#ifdef CONFIG_AUDIT
Implement the watch_key security hook in Smack to make sure that a key
grants the caller Read permission in order to set a watch on a key.
Also implement the post_notification security hook to make sure that the
notification source is granted Write permission by the watch queue.
For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.
Signed-off-by: David Howells <[email protected]>
Acked-by: Casey Schaufler <[email protected]>
---
include/linux/lsm_audit.h | 1 +
security/smack/smack_lsm.c | 82 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 82 insertions(+), 1 deletion(-)
diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 915330abf6e5..734d67889826 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -74,6 +74,7 @@ struct common_audit_data {
#define LSM_AUDIT_DATA_FILE 12
#define LSM_AUDIT_DATA_IBPKEY 13
#define LSM_AUDIT_DATA_IBENDPORT 14
+#define LSM_AUDIT_DATA_NOTIFICATION 15
union {
struct path path;
struct dentry *dentry;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index ecea41ce919b..71b6f37d49c1 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4273,7 +4273,7 @@ static int smack_key_permission(key_ref_t key_ref,
if (tkp == NULL)
return -EACCES;
- if (smack_privileged_cred(CAP_MAC_OVERRIDE, cred))
+ if (smack_privileged(CAP_MAC_OVERRIDE))
return 0;
#ifdef CONFIG_AUDIT
@@ -4319,8 +4319,81 @@ static int smack_key_getsecurity(struct key *key, char **_buffer)
return length;
}
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+/**
+ * smack_watch_key - Smack access to watch a key for notifications.
+ * @key: The key to be watched
+ *
+ * Return 0 if the @watch->cred has permission to read from the key object and
+ * an error otherwise.
+ */
+static int smack_watch_key(struct key *key)
+{
+ struct smk_audit_info ad;
+ struct smack_known *tkp = smk_of_current();
+ int rc;
+
+ if (key == NULL)
+ return -EINVAL;
+ /*
+ * If the key hasn't been initialized give it access so that
+ * it may do so.
+ */
+ if (key->security == NULL)
+ return 0;
+ /*
+ * This should not occur
+ */
+ if (tkp == NULL)
+ return -EACCES;
+
+ if (smack_privileged_cred(CAP_MAC_OVERRIDE, current_cred()))
+ return 0;
+
+#ifdef CONFIG_AUDIT
+ smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_KEY);
+ ad.a.u.key_struct.key = key->serial;
+ ad.a.u.key_struct.key_desc = key->description;
+#endif
+ rc = smk_access(tkp, key->security, MAY_READ, &ad);
+ rc = smk_bu_note("key watch", tkp, key->security, MAY_READ, rc);
+ return rc;
+}
+#endif /* CONFIG_KEY_NOTIFICATIONS */
#endif /* CONFIG_KEYS */
+#ifdef CONFIG_WATCH_QUEUE
+/**
+ * smack_post_notification - Smack access to post a notification to a queue
+ * @w_cred: The credentials of the watcher.
+ * @cred: The credentials of the event source (may be NULL).
+ * @n: The notification message to be posted.
+ */
+static int smack_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ struct smk_audit_info ad;
+ struct smack_known *subj, *obj;
+ int rc;
+
+ /* Always let maintenance notifications through. */
+ if (n->type == WATCH_TYPE_META)
+ return 0;
+
+ if (!cred)
+ return 0;
+ subj = smk_of_task(smack_cred(cred));
+ obj = smk_of_task(smack_cred(w_cred));
+
+ smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_NOTIFICATION);
+ rc = smk_access(subj, obj, MAY_WRITE, &ad);
+ rc = smk_bu_note("notification", subj, obj, MAY_WRITE, rc);
+ return rc;
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
/*
* Smack Audit hooks
*
@@ -4709,8 +4782,15 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(key_free, smack_key_free),
LSM_HOOK_INIT(key_permission, smack_key_permission),
LSM_HOOK_INIT(key_getsecurity, smack_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+ LSM_HOOK_INIT(watch_key, smack_watch_key),
+#endif
#endif /* CONFIG_KEYS */
+#ifdef CONFIG_WATCH_QUEUE
+ LSM_HOOK_INIT(post_notification, smack_post_notification),
+#endif
+
/* Audit hooks */
#ifdef CONFIG_AUDIT
LSM_HOOK_INIT(audit_rule_init, smack_audit_rule_init),
Allow a buffer to be marked such that read() must return the entire buffer
in one go or return ENOBUFS. Multiple buffers can be amalgamated into a
single read, but a short read will occur if the next "whole" buffer won't
fit.
This is useful for watch queue notifications to make sure we don't split a
notification across multiple reads, especially given that we need to
fabricate an overrun record under some circumstances - and that isn't in
the buffers.
Signed-off-by: David Howells <[email protected]>
---
fs/pipe.c | 8 +++++++-
include/linux/pipe_fs_i.h | 1 +
kernel/watch_queue.c | 2 +-
samples/watch_queue/watch_test.c | 2 +-
4 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 5352c07be47f..05d0b02ed08d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -317,8 +317,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
size_t written;
int error;
- if (chars > total_len)
+ if (chars > total_len) {
+ if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
+ if (ret == 0)
+ ret = -ENOBUFS;
+ break;
+ }
chars = total_len;
+ }
error = pipe_buf_confirm(pipe, buf);
if (error) {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index cef70acd99bf..f86ae087aaca 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -8,6 +8,7 @@
#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
+#define PIPE_BUF_FLAG_WHOLE 0x10 /* read() must return entire buffer or error */
/**
* struct pipe_buffer - a linux kernel pipe buffer
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index e2e3344a2586..a01f2fed0983 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -115,7 +115,7 @@ static bool post_one_notification(struct watch_queue *wqueue,
buf->ops = &watch_queue_pipe_buf_ops;
buf->offset = offset;
buf->len = len;
- buf->flags = 0;
+ buf->flags = PIPE_BUF_FLAG_WHOLE;
pipe->head = head + 1;
if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 9bf60abf5c7e..924e13a49c37 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -63,7 +63,7 @@ static void saw_key_change(struct watch_notification *n, size_t len)
*/
static void consumer(int fd)
{
- unsigned char buffer[4096], *p, *end;
+ unsigned char buffer[433], *p, *end;
union {
struct watch_notification n;
unsigned char buf1[128];
So I no longer hate the implementation, but I do want to see the
actual user space users come out of the woodwork and try this out for
their use cases.
I'd hate to see a new event queue interface that people then can't
really use due to it not fulfilling their needs, or can't use for some
other reason.
We've had a fair number of kernel interfaces that ended up not being
used all that much, but had one or two minor users and ended up being
nasty long-term maintenance issues.. I don't want this to become yet
another such one.
Linus
Linus Torvalds <[email protected]> wrote:
> So I no longer hate the implementation, but I do want to see the
> actual user space users come out of the woodwork and try this out for
> their use cases.
I'll see if I can get someone to help fix this:
https://bugzilla.redhat.com/show_bug.cgi?id=1551648
for the KEYRING kerberos cache using notifications. Note that the primary
thrust of this BZ is with KCM cache, but it affects KEYRING as well.
Also, I'll poke Greg, since he was interested in using it for USB
notifications.
David
On Wed, Jan 15, 2020 at 01:31:38PM +0000, David Howells wrote:
> The sample program is run like:
>
> ./samples/watch_queue/watch_test
>
> and watches "/" for mount changes and the current session keyring for key
> changes:
>
> # keyctl add user a a @s
> 1035096409
> # keyctl unlink 1035096409 @s
>
> producing:
>
> # ./watch_test
> read() = 16
> NOTIFY[000]: ty=000001 sy=02 i=00000110
> KEY 2ffc2e5d change=2[linked] aux=1035096409
> read() = 16
> NOTIFY[000]: ty=000001 sy=02 i=00000110
> KEY 2ffc2e5d change=3[unlinked] aux=1035096409
>
> Other events may be produced, such as with a failing disk:
>
> read() = 22
> NOTIFY[000]: ty=000003 sy=02 i=00000416
> USB 3-7.7 dev-reset e=0 r=0
> read() = 24
> NOTIFY[000]: ty=000002 sy=06 i=00000418
> BLOCK 00800050 e=6[critical medium] s=64000ef8
>
> This corresponds to:
>
> blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
>
> in dmesg.
>
> Signed-off-by: David Howells <[email protected]>
mips:allmodconfig:
samples/watch_queue/watch_test.c: In function ‘keyctl_watch_key’:
samples/watch_queue/watch_test.c:34:17: error: ‘__NR_keyctl’ undeclared
Guenter
Hi,
I only just now noticed this work after Dave Chinner pointed towards the
feature in the email leading to
https://lore.kernel.org/linux-fsdevel/[email protected]/
On 2020-01-15 12:10:32 -0800, Linus Torvalds wrote:
> So I no longer hate the implementation, but I do want to see the
> actual user space users come out of the woodwork and try this out for
> their use cases.
Postgres has been looking for something roughly like this, fwiw (or
well, been forced to).
While it's better than it used to be (due to b4678df184b3), we still
have problems to reliably detect buffered IO errors, especially when
done across multiple processes. We can't easily keep an fd open that
predates all writes to a file until, and ensure that fsyncs will happen
only on that fd. The primary reasons for that are
1) every connection (& some internal jobs) is a process, and neither do
want to to fsyncing each touched file in short-lived connections, nor is
it desirable to have to add the complication of having to transfer fds
between processes just to reliably get an error in fsync().
2) we have to cope with having more files open than allowed, so we have
a layer that limits the number of OS level FDs open at the same time. We
don't want to fsync whenever we have to juggle open fds though, as
that'd be too costly.
So it'd good to have a way to *reliably* know when writeback io failed,
so we can abort a checkpoint if necessary, and instead perform journal
replay.
For our purposes we'd probably want errors on the fs/superblock level,
rather than block devices. It's not always easy to map between blockdevs
and relevant filesystems, there are errors above the block layer, and we
definitely don'tt want to crash & restart a database just because
somebody pulled an USB storage device that didn't have any of the
database's data on it.
An earlier version of this patchset had some support for that, albeit
perhaps not fully implemented (no errors raised, afaict?):
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?h=notifications&id=338eec77a0cb29a7d2ae9350066c1990408ae58e
Is the plan to pick this up again once the basic feature is in?
A few notes from the email referenced above (that actually seem to belong
into this thread more than the other:
1) From the angle of reliably needing to detect writeback errors, I find it
somewhat concerning that an LSM may end up entirely filtering away error
notifications, without a consumer being able to detect that:
+void __post_watch_notification(struct watch_list *wlist,
+ struct watch_notification *n,
+ const struct cred *cred,
+ u64 id)
+{
...
+ if (security_post_notification(watch->cred, cred, n) < 0)
+ continue;
It's an unpleasant thought that an overly restrictive [-ly configured]
LSM could lead to silently swallowing data integrity errors.
2) It'd be good if there were documentation, aimed at userland consumers
of this, explaining what the delivery guarantees are. To be useful for
us, it needs to be guaranteed that consuming all notifications ensures
that there are no pending notifications queued up somewhere (so we can
do fsync(data); fsync(journal); check_for_errors();
durable_rename(checkpoint_state.tmp, checkpoint_state);).
3) What will the permission model for accessing the notifications be?
It seems currently anyone, even within a container/namespace or
something, will see blockdev errors from everywhere? The earlier
superblock support (I'm not sure I like that name btw, hard to
understand for us userspace folks), seems to have required exec
permission, but nothing else.
Greetings,
Andres Freund