Hi Markus, Marc,
Here's a set of fixes to improve the interaction of arbitrary lookups in
the AFS dynamic root that hit DNS lookup failures[1]:
(1) Always delete unused (particularly negative) dentries as soon as
possible so that they don't prevent future lookups from retrying.
(2) Fix the handling of new-style negative DNS lookups in ->lookup() to
make them return ENOENT so that userspace doesn't get confused when
stat succeeds but the following open on the looked up file then fails.
(3) Fix key handling so that DNS lookup results are reclaimed as soon as
they expire rather than sitting round either forever or for an
additional 5 mins beyond a set expiry time returning EKEYEXPIRED.
The patches can be found here:
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-fixes
Thanks,
David
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216637 [1]
Link: https://lore.kernel.org/r/[email protected]/ # v1
Link: https://lore.kernel.org/r/[email protected]/ # v2
Link: https://lore.kernel.org/r/[email protected]/ # v3
Changes
=======
ver #4)
- Reduce the negative timeout from 10s to 1s.
ver #3)
- Rebased to v6.7-rc5 which has an additional afs patch.
- Don't add to TIME64_MAX (ie. permanent) when checking expiry time.
ver #2)
- Fix signed-unsigned comparison when checking return val.
David Howells (3):
afs: Fix the dynamic root's d_delete to always delete unused dentries
afs: Fix dynamic root lookup DNS check
keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on
expiry
fs/afs/dynroot.c | 31 +++++++++++++++++--------------
include/linux/key-type.h | 1 +
net/dns_resolver/dns_key.c | 10 +++++++++-
security/keys/gc.c | 31 +++++++++++++++++++++----------
security/keys/internal.h | 11 ++++++++++-
security/keys/key.c | 15 +++++----------
security/keys/proc.c | 2 +-
7 files changed, 64 insertions(+), 37 deletions(-)
Fix the afs dynamic root's d_delete function to always delete unused
dentries rather than only deleting them if they're positive. With things
as they stand upstream, negative dentries stemming from failed DNS lookups
stick around preventing retries.
Fixes: 66c7e1d319a5 ("afs: Split the dynroot stuff out and give it its own ops tables")
Signed-off-by: David Howells <[email protected]>
Tested-by: Markus Suvanto <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
---
fs/afs/dynroot.c | 13 +------------
1 file changed, 1 insertion(+), 12 deletions(-)
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index 1fa8cf23bd36..34474a061654 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -252,20 +252,9 @@ static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
return 1;
}
-/*
- * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
- * sleep)
- * - called from dput() when d_count is going to 0.
- * - return 1 to request dentry be unhashed, 0 otherwise
- */
-static int afs_dynroot_d_delete(const struct dentry *dentry)
-{
- return d_really_is_positive(dentry);
-}
-
const struct dentry_operations afs_dynroot_dentry_operations = {
.d_revalidate = afs_dynroot_d_revalidate,
- .d_delete = afs_dynroot_d_delete,
+ .d_delete = always_delete_dentry,
.d_release = afs_d_release,
.d_automount = afs_d_automount,
};
In the afs dynamic root directory, the ->lookup() function does a DNS check
on the cell being asked for and if the DNS upcall reports an error it will
report an error back to userspace (typically ENOENT).
However, if a failed DNS upcall returns a new-style result, it will return
a valid result, with the status field set appropriately to indicate the
type of failure - and in that case, dns_query() doesn't return an error and
we let stat() complete with no error - which can cause confusion in
userspace as subsequent calls that trigger d_automount then fail with
ENOENT.
Fix this by checking the status result from a valid dns_query() and
returning an error if it indicates a failure.
Fixes: bbb4c4323a4d ("dns: Allow the dns resolver to retrieve a server set")
Reported-by: Markus Suvanto <[email protected]>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=216637
Signed-off-by: David Howells <[email protected]>
Tested-by: Markus Suvanto <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
---
Notes:
Changes
=======
ver #2)
- Fix signed-unsigned comparison when checking return val.
fs/afs/dynroot.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index 34474a061654..1f656005018e 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -114,6 +114,7 @@ static int afs_probe_cell_name(struct dentry *dentry)
struct afs_net *net = afs_d2net(dentry);
const char *name = dentry->d_name.name;
size_t len = dentry->d_name.len;
+ char *result = NULL;
int ret;
/* Names prefixed with a dot are R/W mounts. */
@@ -131,9 +132,22 @@ static int afs_probe_cell_name(struct dentry *dentry)
}
ret = dns_query(net->net, "afsdb", name, len, "srv=1",
- NULL, NULL, false);
- if (ret == -ENODATA || ret == -ENOKEY)
+ &result, NULL, false);
+ if (ret == -ENODATA || ret == -ENOKEY || ret == 0)
ret = -ENOENT;
+ if (ret > 0 && ret >= sizeof(struct dns_server_list_v1_header)) {
+ struct dns_server_list_v1_header *v1 = (void *)result;
+
+ if (v1->hdr.zero == 0 &&
+ v1->hdr.content == DNS_PAYLOAD_IS_SERVER_LIST &&
+ v1->hdr.version == 1 &&
+ (v1->status != DNS_LOOKUP_GOOD &&
+ v1->status != DNS_LOOKUP_GOOD_WITH_BAD))
+ return -ENOENT;
+
+ }
+
+ kfree(result);
return ret;
}
If a key has an expiration time, then when that time passes, the key is
left around for a certain amount of time before being collected (5 mins by
default) so that EKEYEXPIRED can be returned instead of ENOKEY. This is a
problem for DNS keys because we want to redo the DNS lookup immediately at
that point.
Fix this by allowing key types to be marked such that keys of that type
don't have this extra period, but are reclaimed as soon as they expire and
turn this on for dns_resolver-type keys. To make this easier to handle,
key->expiry is changed to be permanent if TIME64_MAX rather than 0.
Furthermore, give such new-style negative DNS results a 1s default expiry
if no other expiry time is set rather than allowing it to stick around
indefinitely. This shouldn't be zero as ls will follow a failing stat call
immediately with a second with AT_SYMLINK_NOFOLLOW added.
Fixes: 1a4240f4764a ("DNS: Separate out CIFS DNS Resolver code")
Signed-off-by: David Howells <[email protected]>
Tested-by: Markus Suvanto <[email protected]>
cc: Wang Lei <[email protected]>
cc: Jeff Layton <[email protected]>
cc: Steve French <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Jarkko Sakkinen <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
---
Notes:
Changes
=======
ver #4)
- Reduce the negative timeout from 10s to 1s.
ver #3)
- Don't add to TIME64_MAX (ie. permanent) when checking expiry time.
include/linux/key-type.h | 1 +
net/dns_resolver/dns_key.c | 10 +++++++++-
security/keys/gc.c | 31 +++++++++++++++++++++----------
security/keys/internal.h | 11 ++++++++++-
security/keys/key.c | 15 +++++----------
security/keys/proc.c | 2 +-
6 files changed, 47 insertions(+), 23 deletions(-)
diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index 7d985a1dfe4a..5caf3ce82373 100644
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -73,6 +73,7 @@ struct key_type {
unsigned int flags;
#define KEY_TYPE_NET_DOMAIN 0x00000001 /* Keys of this type have a net namespace domain */
+#define KEY_TYPE_INSTANT_REAP 0x00000002 /* Keys of this type don't have a delay after expiring */
/* vet a description */
int (*vet_description)(const char *description);
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 01e54b46ae0b..2a6d363763a2 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -91,6 +91,7 @@ const struct cred *dns_resolver_cache;
static int
dns_resolver_preparse(struct key_preparsed_payload *prep)
{
+ const struct dns_server_list_v1_header *v1;
const struct dns_payload_header *bin;
struct user_key_payload *upayload;
unsigned long derrno;
@@ -122,6 +123,13 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
return -EINVAL;
}
+ v1 = (const struct dns_server_list_v1_header *)bin;
+ if ((v1->status != DNS_LOOKUP_GOOD &&
+ v1->status != DNS_LOOKUP_GOOD_WITH_BAD)) {
+ if (prep->expiry == TIME64_MAX)
+ prep->expiry = ktime_get_real_seconds() + 1;
+ }
+
result_len = datalen;
goto store_result;
}
@@ -314,7 +322,7 @@ static long dns_resolver_read(const struct key *key,
struct key_type key_type_dns_resolver = {
.name = "dns_resolver",
- .flags = KEY_TYPE_NET_DOMAIN,
+ .flags = KEY_TYPE_NET_DOMAIN | KEY_TYPE_INSTANT_REAP,
.preparse = dns_resolver_preparse,
.free_preparse = dns_resolver_free_preparse,
.instantiate = generic_key_instantiate,
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 3c90807476eb..eaddaceda14e 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -66,6 +66,19 @@ void key_schedule_gc(time64_t gc_at)
}
}
+/*
+ * Set the expiration time on a key.
+ */
+void key_set_expiry(struct key *key, time64_t expiry)
+{
+ key->expiry = expiry;
+ if (expiry != TIME64_MAX) {
+ if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+ expiry += key_gc_delay;
+ key_schedule_gc(expiry);
+ }
+}
+
/*
* Schedule a dead links collection run.
*/
@@ -176,7 +189,6 @@ static void key_garbage_collector(struct work_struct *work)
static u8 gc_state; /* Internal persistent state */
#define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */
#define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */
-#define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */
#define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */
#define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */
#define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */
@@ -184,21 +196,17 @@ static void key_garbage_collector(struct work_struct *work)
struct rb_node *cursor;
struct key *key;
- time64_t new_timer, limit;
+ time64_t new_timer, limit, expiry;
kenter("[%lx,%x]", key_gc_flags, gc_state);
limit = ktime_get_real_seconds();
- if (limit > key_gc_delay)
- limit -= key_gc_delay;
- else
- limit = key_gc_delay;
/* Work out what we're going to be doing in this pass */
gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2;
gc_state <<= 1;
if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
- gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER;
+ gc_state |= KEY_GC_REAPING_LINKS;
if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
gc_state |= KEY_GC_REAPING_DEAD_1;
@@ -233,8 +241,11 @@ static void key_garbage_collector(struct work_struct *work)
}
}
- if (gc_state & KEY_GC_SET_TIMER) {
- if (key->expiry > limit && key->expiry < new_timer) {
+ expiry = key->expiry;
+ if (expiry != TIME64_MAX) {
+ if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+ expiry += key_gc_delay;
+ if (expiry > limit && expiry < new_timer) {
kdebug("will expire %x in %lld",
key_serial(key), key->expiry - limit);
new_timer = key->expiry;
@@ -276,7 +287,7 @@ static void key_garbage_collector(struct work_struct *work)
*/
kdebug("pass complete");
- if (gc_state & KEY_GC_SET_TIMER && new_timer != (time64_t)TIME64_MAX) {
+ if (new_timer != TIME64_MAX) {
new_timer += key_gc_delay;
key_schedule_gc(new_timer);
}
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 471cf36dedc0..2cffa6dc8255 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -167,6 +167,7 @@ extern unsigned key_gc_delay;
extern void keyring_gc(struct key *keyring, time64_t limit);
extern void keyring_restriction_gc(struct key *keyring,
struct key_type *dead_type);
+void key_set_expiry(struct key *key, time64_t expiry);
extern void key_schedule_gc(time64_t gc_at);
extern void key_schedule_gc_links(void);
extern void key_gc_keytype(struct key_type *ktype);
@@ -215,10 +216,18 @@ extern struct key *key_get_instantiation_authkey(key_serial_t target_id);
*/
static inline bool key_is_dead(const struct key *key, time64_t limit)
{
+ time64_t expiry = key->expiry;
+
+ if (expiry != TIME64_MAX) {
+ if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+ expiry += key_gc_delay;
+ if (expiry <= limit)
+ return true;
+ }
+
return
key->flags & ((1 << KEY_FLAG_DEAD) |
(1 << KEY_FLAG_INVALIDATED)) ||
- (key->expiry > 0 && key->expiry <= limit) ||
key->domain_tag->removed;
}
diff --git a/security/keys/key.c b/security/keys/key.c
index 0260a1902922..5b10641debd5 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -294,6 +294,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
key->uid = uid;
key->gid = gid;
key->perm = perm;
+ key->expiry = TIME64_MAX;
key->restrict_link = restrict_link;
key->last_used_at = ktime_get_real_seconds();
@@ -463,10 +464,7 @@ static int __key_instantiate_and_link(struct key *key,
if (authkey)
key_invalidate(authkey);
- if (prep->expiry != TIME64_MAX) {
- key->expiry = prep->expiry;
- key_schedule_gc(prep->expiry + key_gc_delay);
- }
+ key_set_expiry(key, prep->expiry);
}
}
@@ -606,8 +604,7 @@ int key_reject_and_link(struct key *key,
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);
+ key_set_expiry(key, ktime_get_real_seconds() + timeout);
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
@@ -723,16 +720,14 @@ struct key_type *key_type_lookup(const char *type)
void key_set_timeout(struct key *key, unsigned timeout)
{
- time64_t expiry = 0;
+ time64_t expiry = TIME64_MAX;
/* make the changes with the locks held to prevent races */
down_write(&key->sem);
if (timeout > 0)
expiry = ktime_get_real_seconds() + timeout;
-
- key->expiry = expiry;
- key_schedule_gc(key->expiry + key_gc_delay);
+ key_set_expiry(key, expiry);
up_write(&key->sem);
}
diff --git a/security/keys/proc.c b/security/keys/proc.c
index d0cde6685627..4f4e2c1824f1 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -198,7 +198,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
/* come up with a suitable timeout value */
expiry = READ_ONCE(key->expiry);
- if (expiry == 0) {
+ if (expiry == TIME64_MAX) {
memcpy(xbuf, "perm", 5);
} else if (now >= expiry) {
memcpy(xbuf, "expd", 5);
On 12/21/2023 8:45 AM, David Howells wrote:
> Hi Markus, Marc,
>
> Here's a set of fixes to improve the interaction of arbitrary lookups in
> the AFS dynamic root that hit DNS lookup failures[1]:
>
> (1) Always delete unused (particularly negative) dentries as soon as
> possible so that they don't prevent future lookups from retrying.
>
> (2) Fix the handling of new-style negative DNS lookups in ->lookup() to
> make them return ENOENT so that userspace doesn't get confused when
> stat succeeds but the following open on the looked up file then fails.
>
> (3) Fix key handling so that DNS lookup results are reclaimed as soon as
> they expire rather than sitting round either forever or for an
> additional 5 mins beyond a set expiry time returning EKEYEXPIRED.
>
> The patches can be found here:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-fixes
>
> Thanks,
> David
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216637 [1]
> Link: https://lore.kernel.org/r/[email protected]/ # v1
> Link: https://lore.kernel.org/r/[email protected]/ # v2
> Link: https://lore.kernel.org/r/[email protected]/ # v3
>
> Changes
> =======
> ver #4)
> - Reduce the negative timeout from 10s to 1s.
>
> ver #3)
> - Rebased to v6.7-rc5 which has an additional afs patch.
> - Don't add to TIME64_MAX (ie. permanent) when checking expiry time.
>
> ver #2)
> - Fix signed-unsigned comparison when checking return val.
>
> David Howells (3):
> afs: Fix the dynamic root's d_delete to always delete unused dentries
> afs: Fix dynamic root lookup DNS check
> keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on
> expiry
>
> fs/afs/dynroot.c | 31 +++++++++++++++++--------------
> include/linux/key-type.h | 1 +
> net/dns_resolver/dns_key.c | 10 +++++++++-
> security/keys/gc.c | 31 +++++++++++++++++++++----------
> security/keys/internal.h | 11 ++++++++++-
> security/keys/key.c | 15 +++++----------
> security/keys/proc.c | 2 +-
> 7 files changed, 64 insertions(+), 37 deletions(-)
>
>
> _______________________________________________
> linux-afs mailing list
> http://lists.infradead.org/mailman/listinfo/linux-afs
Reviewed-by: Jeffrey Altman <[email protected]>