Hi,
following is a revised set of the CGroup Namespace patchset which Aditya
Kali has previously sent. The code can also be found in the cgroupns.v7
branch of
https://git.kernel.org/cgit/linux/kernel/git/sergeh/linux-security.git/
To summarize the semantics:
1. CLONE_NEWCGROUP re-uses 0x02000000, which was previously CLONE_STOPPED
2. unsharing a cgroup namespace makes all your current cgroups your new
cgroup root.
3. /proc/pid/cgroup always shows cgroup paths relative to the reader's
cgroup namespce root. A task outside of your cgroup looks like
8:memory:/../../..
4. when a task mounts a cgroupfs, the cgroup which shows up as root depends
on the mounting task's cgroup namespace.
5. setns to a cgroup namespace switches your cgroup namespace but not
your cgroups.
With this, using github.com/hallyn/lxc #2015-11-09/cgns (and
github.com/hallyn/lxcfs #2015-11-10/cgns) we can start a container in a full
proper cgroup namespace, avoiding either cgmanager or lxcfs cgroup bind mounts.
This is completely backward compatible and will be completely invisible
to any existing cgroup users (except for those running inside a cgroup
namespace and looking at /proc/pid/cgroup of tasks outside their
namespace.)
Changes from V6:
1. Switch to some WARN_ONs to provide stack traces
2. Rename kernfs_node_distance to kernfs_depth
3. Make sure kernfs_common_ancestor() nodes are from same root
4. Split kernfs changes for cgroup_mount into separate patch
5. Rename kernfs_obtain_root to kernfs_node_dentry
(And more, see patch changelogs)
Changes from V5:
1. To get a root dentry for cgroup namespace mount, walk the path from the
kernfs root dentry.
Changes from V4:
1. Move the FS_USERNS_MOUNT flag to last patch
2. Rebase onto cgroup/for-4.5
3. Don't non-init user namespaces to bind new subsystems when mounting.
4. Address feedback from Tejun (thanks). Specificaly, not addressed:
. kernfs_obtain_root - walking dentry from kernfs root.
(I think that's the only piece)
5. Dropped unused get_task_cgroup fn/patch.
6. Reworked kernfs_path_from_node_locked() to try to simplify the logic.
It now finds a common ancestor, walks from the source to it, then back
up to the target.
Changes from V3:
1. Rebased onto latest cgroup changes. In particular switch to
css_set_lock and ns_common.
2. Support all hierarchies.
Changes from V2:
1. Added documentation in Documentation/cgroups/namespace.txt
2. Fixed a bug that caused crash
3. Incorporated some other suggestions from last patchset:
- removed use of threadgroup_lock() while creating new cgroupns
- use task_lock() instead of rcu_read_lock() while accessing
task->nsproxy
- optimized setns() to own cgroupns
- simplified code around sane-behavior mount option parsing
4. Restored ACKs from Serge Hallyn from v1 on few patches that have
not changed since then.
Changes from V1:
1. No pinning of processes within cgroupns. Tasks can be freely moved
across cgroups even outside of their cgroupns-root. Usual DAC/MAC policies
apply as before.
2. Path in /proc/<pid>/cgroup is now always shown and is relative to
cgroupns-root. So path can contain '/..' strings depending on cgroupns-root
of the reader and cgroup of <pid>.
3. setns() does not require the process to first move under target
cgroupns-root.
Changes form RFC (V0):
1. setns support for cgroupns
2. 'mount -t cgroup cgroup <mntpt>' from inside a cgroupns now
mounts the cgroup hierarcy with cgroupns-root as the filesystem root.
3. writes to cgroup files outside of cgroupns-root are not allowed
4. visibility of /proc/<pid>/cgroup is further restricted by not showing
anything if the <pid> is in a sibling cgroupns and its cgroup falls outside
your cgroupns-root.
From: Aditya Kali <[email protected]>
The new function kernfs_path_from_node() generates and returns kernfs
path of a given kernfs_node relative to a given parent kernfs_node.
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge E. Hallyn <[email protected]>
---
Changelog 20151125:
- Fully-wing multilinecomments
- Rework kernfs_path_from_node_locked() logic
- Replace BUG_ONs with returning NULL
- Use a const char* for /.. and precalculate its size
Changelog 20151130:
- Update kernfs_path_from_node_locked comment
Changelog 20151208:
- kernfs_node_distance:
* Remove BUG_ON(NULL)s
* Rename kernfs_node_distance to kernfs_depth
- kernfs_common-ancestor:
* Remove useless checks for depth == 0
* Add check to ensure nodes are from same root
- kernfs_path_from_node_locked:
* Remove needless __must_check
* Put p;len on its own decl line.
* Fix wrong WARN_ONCE usage
---
fs/kernfs/dir.c | 177 ++++++++++++++++++++++++++++++++++++++++--------
include/linux/kernfs.h | 3 +
2 files changed, 153 insertions(+), 27 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 91e0045..d1a001a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -44,28 +44,129 @@ static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
}
-static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
- size_t buflen)
+/* kernfs_node_depth - compute depth from @from to @to */
+static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
{
- char *p = buf + buflen;
- int len;
+ size_t depth = 0;
- *--p = '\0';
+ while (to->parent && to != from) {
+ depth++;
+ to = to->parent;
+ }
+ return depth;
+}
- do {
- len = strlen(kn->name);
- if (p - buf < len + 1) {
- buf[0] = '\0';
- p = NULL;
- break;
- }
- p -= len;
- memcpy(p, kn->name, len);
- *--p = '/';
- kn = kn->parent;
- } while (kn && kn->parent);
+static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
+ struct kernfs_node *b)
+{
+ size_t da, db;
+ struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
- return p;
+ if (ra != rb)
+ return NULL;
+
+ da = kernfs_depth(ra->kn, a);
+ db = kernfs_depth(rb->kn, b);
+
+ while (da > db) {
+ a = a->parent;
+ da--;
+ }
+ while (db > da) {
+ b = b->parent;
+ db--;
+ }
+
+ /* worst case b and a will be the same at root */
+ while (b != a) {
+ b = b->parent;
+ a = a->parent;
+ }
+
+ return a;
+}
+
+/**
+ * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
+ * where kn_from is treated as root of the path.
+ * @kn_from: kernfs node which should be treated as root for the path
+ * @kn_to: kernfs node to which path is needed
+ * @buf: buffer to copy the path into
+ * @buflen: size of @buf
+ *
+ * We need to handle couple of scenarios here:
+ * [1] when @kn_from is an ancestor of @kn_to at some level
+ * kn_from: /n1/n2/n3
+ * kn_to: /n1/n2/n3/n4/n5
+ * result: /n4/n5
+ *
+ * [2] when @kn_from is on a different hierarchy and we need to find common
+ * ancestor between @kn_from and @kn_to.
+ * kn_from: /n1/n2/n3/n4
+ * kn_to: /n1/n2/n5
+ * result: /../../n5
+ * OR
+ * kn_from: /n1/n2/n3/n4/n5 [depth=5]
+ * kn_to: /n1/n2/n3 [depth=3]
+ * result: /../..
+ */
+static char *
+kernfs_path_from_node_locked(struct kernfs_node *kn_to,
+ struct kernfs_node *kn_from, char *buf,
+ size_t buflen)
+{
+ char *p = buf;
+ struct kernfs_node *kn, *common;
+ const char parent_str[] = "/..";
+ int i;
+ size_t depth_from, depth_to, len = 0, nlen = 0;
+ size_t plen = sizeof(parent_str) - 1;
+
+ /* We atleast need 2 bytes to write "/\0". */
+ if (buflen < 2)
+ return NULL;
+
+ if (!kn_from)
+ kn_from = kernfs_root(kn_to)->kn;
+
+ if (kn_from == kn_to) {
+ *p = '/';
+ *(++p) = '\0';
+ return buf;
+ }
+
+ common = kernfs_common_ancestor(kn_from, kn_to);
+ if (WARN_ON(!common))
+ return NULL;
+
+ depth_to = kernfs_depth(common, kn_to);
+ depth_from = kernfs_depth(common, kn_from);
+
+ for (i = 0; i < depth_from; i++) {
+ if (len + plen + 1 > buflen)
+ return NULL;
+ strcpy(p, parent_str);
+ p += plen;
+ len += plen;
+ }
+
+ /* Calculate how many bytes we need for the rest */
+ for (kn = kn_to; kn != common; kn = kn->parent)
+ nlen += strlen(kn->name) + 1;
+
+ if (len + nlen + 1 > buflen)
+ return NULL;
+
+ p += nlen;
+ *p = '\0';
+ for (kn = kn_to; kn != common; kn = kn->parent) {
+ nlen = strlen(kn->name);
+ p -= nlen;
+ memcpy(p, kn->name, nlen);
+ *(--p) = '/';
+ }
+
+ return buf;
}
/**
@@ -115,26 +216,48 @@ size_t kernfs_path_len(struct kernfs_node *kn)
}
/**
- * kernfs_path - build full path of a given node
+ * kernfs_path_from_node - build path of node @kn relative to @kn_root.
+ * @kn_root: parent kernfs_node relative to which we need to build the path
* @kn: kernfs_node of interest
- * @buf: buffer to copy @kn's name into
+ * @buf: buffer to copy @kn's path into
* @buflen: size of @buf
*
- * Builds and returns the full path of @kn in @buf of @buflen bytes. The
- * path is built from the end of @buf so the returned pointer usually
- * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
+ * Builds and returns @kn's path relative to @kn_root. @kn_root and @kn must
+ * be on the same kernfs-root. If @kn_root is not parent of @kn, then a relative
+ * path (which includes '..'s) as needed to reach from @kn_root to @kn is
+ * returned.
+ * The path may be built from the end of @buf so the returned pointer may not
+ * match @buf. If @buf isn't long enough, @buf is nul terminated
* and %NULL is returned.
*/
-char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
+char *kernfs_path_from_node(struct kernfs_node *kn_root, struct kernfs_node *kn,
+ char *buf, size_t buflen)
{
unsigned long flags;
char *p;
spin_lock_irqsave(&kernfs_rename_lock, flags);
- p = kernfs_path_locked(kn, buf, buflen);
+ p = kernfs_path_from_node_locked(kn, kn_root, buf, buflen);
spin_unlock_irqrestore(&kernfs_rename_lock, flags);
return p;
}
+EXPORT_SYMBOL_GPL(kernfs_path_from_node);
+
+/**
+ * kernfs_path - build full path of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Builds and returns the full path of @kn in @buf of @buflen bytes. The
+ * path is built from the end of @buf so the returned pointer usually
+ * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
+ * and %NULL is returned.
+ */
+char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ return kernfs_path_from_node(NULL, kn, buf, buflen);
+}
EXPORT_SYMBOL_GPL(kernfs_path);
/**
@@ -168,8 +291,8 @@ void pr_cont_kernfs_path(struct kernfs_node *kn)
spin_lock_irqsave(&kernfs_rename_lock, flags);
- p = kernfs_path_locked(kn, kernfs_pr_cont_buf,
- sizeof(kernfs_pr_cont_buf));
+ p = kernfs_path_from_node_locked(kn, NULL, kernfs_pr_cont_buf,
+ sizeof(kernfs_pr_cont_buf));
if (p)
pr_cont("%s", p);
else
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5d4e9c4..d025ebd 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -267,6 +267,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
size_t kernfs_path_len(struct kernfs_node *kn);
+char * __must_check kernfs_path_from_node(struct kernfs_node *root_kn,
+ struct kernfs_node *kn, char *buf,
+ size_t buflen);
char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
size_t buflen);
void pr_cont_kernfs_name(struct kernfs_node *kn);
--
1.7.9.5
From: Aditya Kali <[email protected]>
CLONE_NEWCGROUP will be used to create new cgroup namespace.
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge Hallyn <[email protected]>
---
include/uapi/linux/sched.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index cc89dde..5f0fe01 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -21,8 +21,7 @@
#define CLONE_DETACHED 0x00400000 /* Unused, ignored */
#define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */
#define CLONE_CHILD_SETTID 0x01000000 /* set the TID in the child */
-/* 0x02000000 was previously the unused CLONE_STOPPED (Start in stopped state)
- and is now available for re-use. */
+#define CLONE_NEWCGROUP 0x02000000 /* New cgroup namespace */
#define CLONE_NEWUTS 0x04000000 /* New utsname namespace */
#define CLONE_NEWIPC 0x08000000 /* New ipc namespace */
#define CLONE_NEWUSER 0x10000000 /* New user namespace */
--
1.7.9.5
From: Aditya Kali <[email protected]>
Introduce the ability to create new cgroup namespace. The newly created
cgroup namespace remembers the cgroup of the process at the point
of creation of the cgroup namespace (referred as cgroupns-root).
The main purpose of cgroup namespace is to virtualize the contents
of /proc/self/cgroup file. Processes inside a cgroup namespace
are only able to see paths relative to their namespace root
(unless they are moved outside of their cgroupns-root, at which point
they will see a relative path from their cgroupns-root).
For a correctly setup container this enables container-tools
(like libcontainer, lxc, lmctfy, etc.) to create completely virtualized
containers without leaking system level cgroup hierarchy to the task.
This patch only implements the 'unshare' part of the cgroupns.
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge Hallyn <[email protected]>
---
Changelog: 2015-11-24
- move cgroup_namespace.c into cgroup.c (and .h)
- reformatting
- make get_cgroup_ns return void
- rename ns->root_cgrps to root_cset.
Changelog: 2015-12-08
- Move init_cgroup_ns to other variable declarations
- Remove accidental conversion of put-css_set to inline
- Drop BUG_ON(NULL)
- Remove unneeded pre declaration of struct cgroupns_operations.
- cgroup.h: collect common ns declerations
---
fs/proc/namespaces.c | 3 +
include/linux/cgroup.h | 54 ++++++++++++++++--
include/linux/nsproxy.h | 2 +
include/linux/proc_ns.h | 4 ++
kernel/cgroup.c | 146 ++++++++++++++++++++++++++++++++++++++++++++++-
kernel/fork.c | 2 +-
kernel/nsproxy.c | 21 ++++++-
7 files changed, 220 insertions(+), 12 deletions(-)
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index f6e8354..bd61075 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -28,6 +28,9 @@ static const struct proc_ns_operations *ns_entries[] = {
&userns_operations,
#endif
&mntns_operations,
+#ifdef CONFIG_CGROUPS
+ &cgroupns_operations,
+#endif
};
static const char *proc_ns_follow_link(struct dentry *dentry, void **cookie)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 2b3e2314..906e348 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -17,9 +17,57 @@
#include <linux/seq_file.h>
#include <linux/kernfs.h>
#include <linux/jump_label.h>
+#include <linux/nsproxy.h>
+#include <linux/types.h>
+#include <linux/ns_common.h>
+#include <linux/nsproxy.h>
+#include <linux/user_namespace.h>
#include <linux/cgroup-defs.h>
+struct cgroup_namespace {
+ atomic_t count;
+ struct ns_common ns;
+ struct user_namespace *user_ns;
+ struct css_set *root_cset;
+};
+
+extern struct cgroup_namespace init_cgroup_ns;
+
+#ifdef CONFIG_CGROUPS
+
+void free_cgroup_ns(struct cgroup_namespace *ns);
+
+struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
+ struct user_namespace *user_ns,
+ struct cgroup_namespace *old_ns);
+
+char * cgroup_path(struct cgroup *cgrp, char *buf, size_t buflen);
+
+#else /* !CONFIG_CGROUPS */
+
+static inline void free_cgroup_ns(struct cgroup_namespace *ns) { }
+static inline struct cgroup_namespace *
+copy_cgroup_ns(unsigned long flags, struct user_namespace *user_ns,
+ struct cgroup_namespace *old_ns)
+{
+ return old_ns;
+}
+
+#endif /* !CONFIG_CGROUPS */
+
+static inline void get_cgroup_ns(struct cgroup_namespace *ns)
+{
+ if (ns)
+ atomic_inc(&ns->count);
+}
+
+static inline void put_cgroup_ns(struct cgroup_namespace *ns)
+{
+ if (ns && atomic_dec_and_test(&ns->count))
+ free_cgroup_ns(ns);
+}
+
#ifdef CONFIG_CGROUPS
/*
@@ -509,12 +557,6 @@ static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
return kernfs_name(cgrp->kn, buf, buflen);
}
-static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
- size_t buflen)
-{
- return kernfs_path(cgrp->kn, buf, buflen);
-}
-
static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
{
pr_cont_kernfs_name(cgrp->kn);
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 35fa08f..ac0d65b 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -8,6 +8,7 @@ struct mnt_namespace;
struct uts_namespace;
struct ipc_namespace;
struct pid_namespace;
+struct cgroup_namespace;
struct fs_struct;
/*
@@ -33,6 +34,7 @@ struct nsproxy {
struct mnt_namespace *mnt_ns;
struct pid_namespace *pid_ns_for_children;
struct net *net_ns;
+ struct cgroup_namespace *cgroup_ns;
};
extern struct nsproxy init_nsproxy;
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index 42dfc61..de0e771 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -9,6 +9,8 @@
struct pid_namespace;
struct nsproxy;
struct path;
+struct task_struct;
+struct inode;
struct proc_ns_operations {
const char *name;
@@ -24,6 +26,7 @@ extern const struct proc_ns_operations ipcns_operations;
extern const struct proc_ns_operations pidns_operations;
extern const struct proc_ns_operations userns_operations;
extern const struct proc_ns_operations mntns_operations;
+extern const struct proc_ns_operations cgroupns_operations;
/*
* We always define these enumerators
@@ -34,6 +37,7 @@ enum {
PROC_UTS_INIT_INO = 0xEFFFFFFEU,
PROC_USER_INIT_INO = 0xEFFFFFFDU,
PROC_PID_INIT_INO = 0xEFFFFFFCU,
+ PROC_CGROUP_INIT_INO = 0xEFFFFFFBU,
};
#ifdef CONFIG_PROC_FS
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7f2f007..92db64c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -57,6 +57,9 @@
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
#include <linux/kthread.h>
#include <linux/delay.h>
+#include <linux/proc_ns.h>
+#include <linux/nsproxy.h>
+#include <linux/proc_ns.h>
#include <linux/atomic.h>
@@ -208,6 +211,15 @@ static unsigned long have_fork_callback __read_mostly;
static unsigned long have_exit_callback __read_mostly;
static unsigned long have_free_callback __read_mostly;
+/* Cgroup namespace for init task */
+struct cgroup_namespace init_cgroup_ns = {
+ .count = { .counter = 1, },
+ .user_ns = &init_user_ns,
+ .ns.ops = &cgroupns_operations,
+ .ns.inum = PROC_CGROUP_INIT_INO,
+ .root_cset = &init_css_set,
+};
+
/* Ditto for the can_fork callback. */
static unsigned long have_canfork_callback __read_mostly;
@@ -430,18 +442,18 @@ static inline bool cgroup_is_dead(const struct cgroup *cgrp)
return !(cgrp->self.flags & CSS_ONLINE);
}
-static void cgroup_get(struct cgroup *cgrp)
+static inline void cgroup_get(struct cgroup *cgrp)
{
WARN_ON_ONCE(cgroup_is_dead(cgrp));
css_get(&cgrp->self);
}
-static bool cgroup_tryget(struct cgroup *cgrp)
+static inline bool cgroup_tryget(struct cgroup *cgrp)
{
return css_tryget(&cgrp->self);
}
-static void cgroup_put(struct cgroup *cgrp)
+static inline void cgroup_put(struct cgroup *cgrp)
{
css_put(&cgrp->self);
}
@@ -2189,6 +2201,22 @@ static struct file_system_type cgroup2_fs_type = {
.kill_sb = cgroup_kill_sb,
};
+static char * cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
+ struct cgroup_namespace *ns)
+{
+ struct cgroup *root;
+
+ root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
+ return kernfs_path_from_node(root->kn, cgrp->kn, buf, buflen);
+}
+
+char * cgroup_path(struct cgroup *cgrp, char *buf, size_t buflen)
+{
+ return cgroup_path_ns(cgrp, buf, buflen,
+ current->nsproxy->cgroup_ns);
+}
+EXPORT_SYMBOL_GPL(cgroup_path);
+
/**
* task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
* @task: target task
@@ -5289,6 +5317,8 @@ int __init cgroup_init(void)
BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
+ get_user_ns(init_cgroup_ns.user_ns);
+
mutex_lock(&cgroup_mutex);
/* Add init_css_set to the hash table */
@@ -5805,6 +5835,116 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
}
+/* cgroup namespaces */
+
+static struct cgroup_namespace *alloc_cgroup_ns(void)
+{
+ struct cgroup_namespace *new_ns;
+ int ret;
+
+ new_ns = kzalloc(sizeof(struct cgroup_namespace), GFP_KERNEL);
+ if (!new_ns)
+ return ERR_PTR(-ENOMEM);
+ ret = ns_alloc_inum(&new_ns->ns);
+ if (ret) {
+ kfree(new_ns);
+ return ERR_PTR(ret);
+ }
+ atomic_set(&new_ns->count, 1);
+ new_ns->ns.ops = &cgroupns_operations;
+ return new_ns;
+}
+
+void free_cgroup_ns(struct cgroup_namespace *ns)
+{
+ put_css_set(ns->root_cset);
+ put_user_ns(ns->user_ns);
+ ns_free_inum(&ns->ns);
+ kfree(ns);
+}
+EXPORT_SYMBOL(free_cgroup_ns);
+
+struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
+ struct user_namespace *user_ns,
+ struct cgroup_namespace *old_ns)
+{
+ struct cgroup_namespace *new_ns = NULL;
+ struct css_set *cset = NULL;
+ int err;
+
+ BUG_ON(!old_ns);
+
+ if (!(flags & CLONE_NEWCGROUP)) {
+ get_cgroup_ns(old_ns);
+ return old_ns;
+ }
+
+ /* Allow only sysadmin to create cgroup namespace. */
+ err = -EPERM;
+ if (!ns_capable(user_ns, CAP_SYS_ADMIN))
+ goto err_out;
+
+ cset = task_css_set(current);
+ get_css_set(cset);
+
+ err = -ENOMEM;
+ new_ns = alloc_cgroup_ns();
+ if (!new_ns)
+ goto err_out;
+
+ new_ns->user_ns = get_user_ns(user_ns);
+ new_ns->root_cset = cset;
+
+ return new_ns;
+
+err_out:
+ if (cset)
+ put_css_set(cset);
+ kfree(new_ns);
+ return ERR_PTR(err);
+}
+
+static int cgroupns_install(struct nsproxy *nsproxy, void *ns)
+{
+ pr_info("setns not supported for cgroup namespace");
+ return -EINVAL;
+}
+
+static struct ns_common *cgroupns_get(struct task_struct *task)
+{
+ struct cgroup_namespace *ns = NULL;
+ struct nsproxy *nsproxy;
+
+ task_lock(task);
+ nsproxy = task->nsproxy;
+ if (nsproxy) {
+ ns = nsproxy->cgroup_ns;
+ get_cgroup_ns(ns);
+ }
+ task_unlock(task);
+
+ return ns ? &ns->ns : NULL;
+}
+
+static void cgroupns_put(struct ns_common *ns)
+{
+ put_cgroup_ns(to_cg_ns(ns));
+}
+
+const struct proc_ns_operations cgroupns_operations = {
+ .name = "cgroup",
+ .type = CLONE_NEWCGROUP,
+ .get = cgroupns_get,
+ .put = cgroupns_put,
+ .install = cgroupns_install,
+};
+
+static __init int cgroup_namespaces_init(void)
+{
+ return 0;
+}
+subsys_initcall(cgroup_namespaces_init);
+
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *
debug_css_alloc(struct cgroup_subsys_state *parent_css)
diff --git a/kernel/fork.c b/kernel/fork.c
index ba7d1c0..7982fee 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1880,7 +1880,7 @@ static int check_unshare_flags(unsigned long unshare_flags)
if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
- CLONE_NEWUSER|CLONE_NEWPID))
+ CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
return -EINVAL;
/*
* Not implemented, but pretend it works if there is nothing
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 49746c8..64fe865 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -25,6 +25,7 @@
#include <linux/proc_ns.h>
#include <linux/file.h>
#include <linux/syscalls.h>
+#include <linux/cgroup.h>
static struct kmem_cache *nsproxy_cachep;
@@ -39,6 +40,9 @@ struct nsproxy init_nsproxy = {
#ifdef CONFIG_NET
.net_ns = &init_net,
#endif
+#ifdef CONFIG_CGROUPS
+ .cgroup_ns = &init_cgroup_ns,
+#endif
};
static inline struct nsproxy *create_nsproxy(void)
@@ -92,6 +96,13 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
goto out_pid;
}
+ new_nsp->cgroup_ns = copy_cgroup_ns(flags, user_ns,
+ tsk->nsproxy->cgroup_ns);
+ if (IS_ERR(new_nsp->cgroup_ns)) {
+ err = PTR_ERR(new_nsp->cgroup_ns);
+ goto out_cgroup;
+ }
+
new_nsp->net_ns = copy_net_ns(flags, user_ns, tsk->nsproxy->net_ns);
if (IS_ERR(new_nsp->net_ns)) {
err = PTR_ERR(new_nsp->net_ns);
@@ -101,6 +112,9 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
return new_nsp;
out_net:
+ if (new_nsp->cgroup_ns)
+ put_cgroup_ns(new_nsp->cgroup_ns);
+out_cgroup:
if (new_nsp->pid_ns_for_children)
put_pid_ns(new_nsp->pid_ns_for_children);
out_pid:
@@ -128,7 +142,8 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
struct nsproxy *new_ns;
if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
- CLONE_NEWPID | CLONE_NEWNET)))) {
+ CLONE_NEWPID | CLONE_NEWNET |
+ CLONE_NEWCGROUP)))) {
get_nsproxy(old_ns);
return 0;
}
@@ -165,6 +180,8 @@ void free_nsproxy(struct nsproxy *ns)
put_ipc_ns(ns->ipc_ns);
if (ns->pid_ns_for_children)
put_pid_ns(ns->pid_ns_for_children);
+ if (ns->cgroup_ns)
+ put_cgroup_ns(ns->cgroup_ns);
put_net(ns->net_ns);
kmem_cache_free(nsproxy_cachep, ns);
}
@@ -180,7 +197,7 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
int err = 0;
if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
- CLONE_NEWNET | CLONE_NEWPID)))
+ CLONE_NEWNET | CLONE_NEWPID | CLONE_NEWCGROUP)))
return 0;
user_ns = new_cred ? new_cred->user_ns : current_user_ns();
--
1.7.9.5
From: Aditya Kali <[email protected]>
setns on a cgroup namespace is allowed only if
task has CAP_SYS_ADMIN in its current user-namespace and
over the user-namespace associated with target cgroupns.
No implicit cgroup changes happen with attaching to another
cgroupns. It is expected that the somone moves the attaching
process under the target cgroupns-root.
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge E. Hallyn <[email protected]>
---
kernel/cgroup.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 92db64c..f34551a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5904,10 +5904,28 @@ err_out:
return ERR_PTR(err);
}
-static int cgroupns_install(struct nsproxy *nsproxy, void *ns)
+static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
{
- pr_info("setns not supported for cgroup namespace");
- return -EINVAL;
+ return container_of(ns, struct cgroup_namespace, ns);
+}
+
+static int cgroupns_install(struct nsproxy *nsproxy, struct ns_common *ns)
+{
+ struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
+
+ if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) ||
+ !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /* Don't need to do anything if we are attaching to our own cgroupns. */
+ if (cgroup_ns == nsproxy->cgroup_ns)
+ return 0;
+
+ get_cgroup_ns(cgroup_ns);
+ put_cgroup_ns(nsproxy->cgroup_ns);
+ nsproxy->cgroup_ns = cgroup_ns;
+
+ return 0;
}
static struct ns_common *cgroupns_get(struct task_struct *task)
--
1.7.9.5
From: Aditya Kali <[email protected]>
Add a new kernfs api is added to lookup the dentry for a particular
kernfs path.
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge E. Hallyn <[email protected]>
---
Changelog:
20151116 - Don't allow user namespaces to bind new subsystems
20151118 - postpone the FS_USERNS_MOUNT flag until the
last patch, until we can convince ourselves it
is safe.
20151207 - Switch to walking up the kernfs path from kn root.
20151208 - Split out the kernfs change
- Style changes
- Switch from pr_crit to WARN_ON
- Reorder arguments to kernfs_obtain_root
- rename kernfs_obtain_root to kernfs_node_dentry
---
fs/kernfs/mount.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/kernfs.h | 2 ++
2 files changed, 69 insertions(+)
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 8eaf417..7224296 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -14,6 +14,7 @@
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
+#include <linux/namei.h>
#include "kernfs-internal.h"
@@ -62,6 +63,72 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
return NULL;
}
+/*
+ * find the next ancestor in the path down to @child, where @parent was the
+ * ancestor whose descendant we want to find.
+ *
+ * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
+ * node. If @parent is b, then we return the node for c.
+ * Passing in d as @parent is not ok.
+ */
+static struct kernfs_node *
+find_next_ancestor(struct kernfs_node *child, struct kernfs_node *parent)
+{
+ if (child == parent) {
+ pr_crit_once("BUG in find_next_ancestor: called with parent == child");
+ return NULL;
+ }
+
+ while (child->parent != parent) {
+ if (!child->parent)
+ return NULL;
+ child = child->parent;
+ }
+
+ return child;
+}
+
+/**
+ * kernfs_node_dentry - get a dentry for the given kernfs_node
+ * @kn: kernfs_node for which a dentry is needed
+ * @sb: the kernfs super_block
+ */
+struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
+ struct super_block *sb)
+{
+ struct dentry *dentry;
+ struct kernfs_node *knparent = NULL;
+
+ BUG_ON(sb->s_op != &kernfs_sops);
+
+ dentry = dget(sb->s_root);
+
+ /* Check if this is the root kernfs_node */
+ if (!kn->parent)
+ return dentry;
+
+ knparent = find_next_ancestor(kn, NULL);
+ if (WARN_ON(!knparent))
+ return ERR_PTR(-EINVAL);
+
+ do {
+ struct dentry *dtmp;
+ struct kernfs_node *kntmp;
+
+ if (kn == knparent)
+ return dentry;
+ kntmp = find_next_ancestor(kn, knparent);
+ if (WARN_ON(!kntmp))
+ return ERR_PTR(-EINVAL);
+ dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
+ dput(dentry);
+ if (IS_ERR(dtmp))
+ return dtmp;
+ knparent = kntmp;
+ dentry = dtmp;
+ } while (1);
+}
+
static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
{
struct kernfs_super_info *info = kernfs_info(sb);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index d025ebd..6eba888 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -284,6 +284,8 @@ struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
+struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
+ struct super_block *sb);
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
--
1.7.9.5
From: Serge Hallyn <[email protected]>
This patch enables cgroup mounting inside userns when a process
as appropriate privileges. The cgroup filesystem mounted is
rooted at the cgroupns-root. Thus, in a container-setup, only
the hierarchy under the cgroupns-root is exposed inside the container.
This allows container management tools to run inside the containers
without depending on any global state.
Signed-off-by: Serge Hallyn <[email protected]>
---
Changelog:
20151116 - Don't allow user namespaces to bind new subsystems
20151118 - postpone the FS_USERNS_MOUNT flag until the
last patch, until we can convince ourselves it
is safe.
20151207 - Switch to walking up the kernfs path from kn root.
- Group initialized variables
- Explain the capable(CAP_SYS_ADMIN) check
- Style fixes
---
kernel/cgroup.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f34551a..b92b3fd 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2006,6 +2006,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
{
bool is_v2 = fs_type == &cgroup2_fs_type;
struct super_block *pinned_sb = NULL;
+ struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup_subsys *ss;
struct cgroup_root *root;
struct cgroup_sb_opts opts;
@@ -2014,6 +2015,14 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int i;
bool new_sb;
+ get_cgroup_ns(ns);
+
+ /* Check if the caller has permission to mount. */
+ if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
+ put_cgroup_ns(ns);
+ return ERR_PTR(-EPERM);
+ }
+
/*
* The first time anyone tries to mount a cgroup, enable the list
* linking each css_set to its tasks and fix up all existing tasks.
@@ -2129,6 +2138,16 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
goto out_unlock;
}
+ /*
+ * We know this subsystem has not yet been bound. Users in a non-init
+ * user namespace may only mount hierarchies with no bound subsystems,
+ * i.e. 'none,name=user1'
+ */
+ if (!opts.none && !capable(CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ goto out_unlock;
+ }
+
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root) {
ret = -ENOMEM;
@@ -2147,12 +2166,30 @@ out_free:
kfree(opts.release_agent);
kfree(opts.name);
- if (ret)
+ if (ret) {
+ put_cgroup_ns(ns);
return ERR_PTR(ret);
+ }
out_mount:
dentry = kernfs_mount(fs_type, flags, root->kf_root,
is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,
&new_sb);
+
+ /*
+ * In non-init cgroup namespace, instead of root cgroup's
+ * dentry, we return the dentry corresponding to the
+ * cgroupns->root_cgrp.
+ */
+ if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
+ struct dentry *nsdentry;
+ struct cgroup *cgrp;
+
+ cgrp = cset_cgroup_from_root(ns->root_cset, root);
+ nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
+ dput(dentry);
+ dentry = nsdentry;
+ }
+
if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
@@ -2165,6 +2202,7 @@ out_mount:
deactivate_super(pinned_sb);
}
+ put_cgroup_ns(ns);
return dentry;
}
--
1.7.9.5
From: Aditya Kali <[email protected]>
Signed-off-by: Aditya Kali <[email protected]>
Signed-off-by: Serge Hallyn <[email protected]>
---
Changelog (2015-12-08): Merge into Documentation/cgroup.txt
---
Documentation/cgroup.txt | 144 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 144 insertions(+)
diff --git a/Documentation/cgroup.txt b/Documentation/cgroup.txt
index 31d1f7b..ca42df4 100644
--- a/Documentation/cgroup.txt
+++ b/Documentation/cgroup.txt
@@ -47,6 +47,7 @@ CONTENTS
5-3. IO
5-3-1. IO Interface Files
5-3-2. Writeback
+6. Namespaces
P. Information on Kernel Programming
P-1. Filesystem Support for Writeback
D. Deprecated v1 Core Features
@@ -1013,6 +1014,149 @@ writeback as follows.
vm.dirty[_background]_ratio.
+6. CGroup Namespaces
+
+CGroup Namespace provides a mechanism to virtualize the view of the
+/proc/<pid>/cgroup file. The CLONE_NEWCGROUP clone-flag can be used with
+clone() and unshare() syscalls to create a new cgroup namespace.
+The process running inside the cgroup namespace will have its /proc/<pid>/cgroup
+output restricted to cgroupns-root. cgroupns-root is the cgroup of the process
+at the time of creation of the cgroup namespace.
+
+Prior to CGroup Namespace, the /proc/<pid>/cgroup file used to show complete
+path of the cgroup of a process. In a container setup (where a set of cgroups
+and namespaces are intended to isolate processes), the /proc/<pid>/cgroup file
+may leak potential system level information to the isolated processes.
+
+For Example:
+ $ cat /proc/self/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/batchjobs/container_id1
+
+The path '/batchjobs/container_id1' can generally be considered as system-data
+and its desirable to not expose it to the isolated process.
+
+CGroup Namespaces can be used to restrict visibility of this path.
+For Example:
+ # Before creating cgroup namespace
+ $ ls -l /proc/self/ns/cgroup
+ lrwxrwxrwx 1 root root 0 2014-07-15 10:37 /proc/self/ns/cgroup -> cgroup:[4026531835]
+ $ cat /proc/self/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/batchjobs/container_id1
+
+ # unshare(CLONE_NEWCGROUP) and exec /bin/bash
+ $ ~/unshare -c
+ [ns]$ ls -l /proc/self/ns/cgroup
+ lrwxrwxrwx 1 root root 0 2014-07-15 10:35 /proc/self/ns/cgroup -> cgroup:[4026532183]
+ # From within new cgroupns, process sees that its in the root cgroup
+ [ns]$ cat /proc/self/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/
+
+ # From global cgroupns:
+ $ cat /proc/<pid>/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/batchjobs/container_id1
+
+ # Unshare cgroupns along with userns and mountns
+ # Following calls unshare(CLONE_NEWCGROUP|CLONE_NEWUSER|CLONE_NEWNS), then
+ # sets up uid/gid map and execs /bin/bash
+ $ ~/unshare -c -u -m
+ # Originally, we were in /batchjobs/container_id1 cgroup. Mount our own cgroup
+ # hierarchy.
+ [ns]$ mount -t cgroup cgroup /tmp/cgroup
+ [ns]$ ls -l /tmp/cgroup
+ total 0
+ -r--r--r-- 1 root root 0 2014-10-13 09:32 cgroup.controllers
+ -r--r--r-- 1 root root 0 2014-10-13 09:32 cgroup.populated
+ -rw-r--r-- 1 root root 0 2014-10-13 09:25 cgroup.procs
+ -rw-r--r-- 1 root root 0 2014-10-13 09:32 cgroup.subtree_control
+
+The cgroupns-root (/batchjobs/container_id1 in above example) becomes the
+filesystem root for the namespace specific cgroupfs mount.
+
+The virtualization of /proc/self/cgroup file combined with restricting
+the view of cgroup hierarchy by namespace-private cgroupfs mount
+should provide a completely isolated cgroup view inside the container.
+
+In its current form, the cgroup namespaces patcheset provides following
+behavior:
+
+(1) The 'cgroupns-root' for a cgroup namespace is the cgroup in which
+ the process calling unshare is running.
+ For ex. if a process in /batchjobs/container_id1 cgroup calls unshare,
+ cgroup /batchjobs/container_id1 becomes the cgroupns-root.
+ For the init_cgroup_ns, this is the real root ('/') cgroup
+ (identified in code as cgrp_dfl_root.cgrp).
+
+(2) The cgroupns-root cgroup does not change even if the namespace
+ creator process later moves to a different cgroup.
+ $ ~/unshare -c # unshare cgroupns in some cgroup
+ [ns]$ cat /proc/self/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/
+ [ns]$ mkdir sub_cgrp_1
+ [ns]$ echo 0 > sub_cgrp_1/cgroup.procs
+ [ns]$ cat /proc/self/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/sub_cgrp_1
+
+(3) Each process gets its CGROUPNS specific view of /proc/<pid>/cgroup
+(a) Processes running inside the cgroup namespace will be able to see
+ cgroup paths (in /proc/self/cgroup) only inside their root cgroup
+ [ns]$ sleep 100000 & # From within unshared cgroupns
+ [1] 7353
+ [ns]$ echo 7353 > sub_cgrp_1/cgroup.procs
+ [ns]$ cat /proc/7353/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/sub_cgrp_1
+
+(b) From global cgroupns, the real cgroup path will be visible:
+ $ cat /proc/7353/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/batchjobs/container_id1/sub_cgrp_1
+
+(c) From a sibling cgroupns (cgroupns root-ed at a different cgroup), cgroup
+ path relative to its own cgroupns-root will be shown:
+ # ns2's cgroupns-root is at '/batchjobs/container_id2'
+ [ns2]$ cat /proc/7353/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/../container_id2/sub_cgrp_1
+
+ Note that the relative path always starts with '/' to indicate that its
+ relative to the cgroupns-root of the caller.
+
+(4) Processes inside a cgroupns can move in-and-out of the cgroupns-root
+ (if they have proper access to external cgroups).
+ # From inside cgroupns (with cgroupns-root at /batchjobs/container_id1), and
+ # assuming that the global hierarchy is still accessible inside cgroupns:
+ $ cat /proc/7353/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/sub_cgrp_1
+ $ echo 7353 > batchjobs/container_id2/cgroup.procs
+ $ cat /proc/7353/cgroup
+ 0:cpuset,cpu,cpuacct,memory,devices,freezer,hugetlb:/../container_id2
+
+ Note that this kind of setup is not encouraged. A task inside cgroupns
+ should only be exposed to its own cgroupns hierarchy. Otherwise it makes
+ the virtualization of /proc/<pid>/cgroup less useful.
+
+(5) Setns to another cgroup namespace is allowed when:
+ (a) the process has CAP_SYS_ADMIN in its current userns
+ (b) the process has CAP_SYS_ADMIN in the target cgroupns' userns
+ No implicit cgroup changes happen with attaching to another cgroupns. It
+ is expected that the somone moves the attaching process under the target
+ cgroupns-root.
+
+(6) When some thread from a multi-threaded process unshares its
+ cgroup-namespace, the new cgroupns gets applied to the entire process (all
+ the threads). For the unified-hierarchy this is expected as it only allows
+ process-level containerization. For the legacy hierarchies this may be
+ unexpected. So all the threads in the process will have the same cgroup.
+
+(7) The cgroup namespace is alive as long as there is atleast 1
+ process inside it. When the last process exits, the cgroup
+ namespace is destroyed. The cgroupns-root and the actual cgroups
+ remain though.
+
+(8) Namespace specific cgroup hierarchy can be mounted by a process running
+ inside cgroupns:
+ $ mount -t cgroup -o __DEVEL__sane_behavior cgroup $MOUNT_POINT
+
+ This will mount the unified cgroup hierarchy with cgroupns-root as the
+ filesystem root. The process needs CAP_SYS_ADMIN in its userns and mntns.
+
P. Information on Kernel Programming
This section contains kernel programming information in the areas
--
1.7.9.5
From: Serge Hallyn <[email protected]>
allowing root in a non-init user namespace to mount it. This should
now be safe, because
1. non-init-root cannot mount a previously unbound subsystem
2. the task doing the mount must be privileged with respect to the
user namespace owning the cgroup namespace
3. the mounted subsystem will have its current cgroup as the root dentry.
the permissions will be unchanged, so tasks will receive no new
privilege over the cgroups which they did not have on the original
mounts.
Signed-off-by: Serge Hallyn <[email protected]>
---
kernel/cgroup.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b92b3fd..7d5d7e1 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2231,12 +2231,14 @@ static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
};
static struct file_system_type cgroup2_fs_type = {
.name = "cgroup2",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
};
static char * cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
--
1.7.9.5
Hello, Serge.
On Wed, Dec 09, 2015 at 01:28:54PM -0600, [email protected] wrote:
> +/* kernfs_node_depth - compute depth from @from to @to */
> +static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
...
> +char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
> +{
> + return kernfs_path_from_node(NULL, kn, buf, buflen);
> +}
...
> diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> index 5d4e9c4..d025ebd 100644
> --- a/include/linux/kernfs.h
> +++ b/include/linux/kernfs.h
> @@ -267,6 +267,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
>
> int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
> size_t kernfs_path_len(struct kernfs_node *kn);
> +char * __must_check kernfs_path_from_node(struct kernfs_node *root_kn,
> + struct kernfs_node *kn, char *buf,
> + size_t buflen);
I think I commented on the same thing before, but I think it'd make
more sense to put @from after @to and the prototype is using @root_kn
which is a bit confusing. Was converting the path functions to return
length too much work? If so, that's fine but please explain what
decisions were made.
I skimmed through the series and spotted several other review points
which didn't get addressed. Can you please go over the previous
review cycle and address the review points?
Thanks.
--
tejun
Quoting Tejun Heo ([email protected]):
> Hello, Serge.
>
> On Wed, Dec 09, 2015 at 01:28:54PM -0600, [email protected] wrote:
> > +/* kernfs_node_depth - compute depth from @from to @to */
> > +static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
> ...
> > +char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
> > +{
> > + return kernfs_path_from_node(NULL, kn, buf, buflen);
> > +}
> ...
> > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> > index 5d4e9c4..d025ebd 100644
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -267,6 +267,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
> >
> > int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
> > size_t kernfs_path_len(struct kernfs_node *kn);
> > +char * __must_check kernfs_path_from_node(struct kernfs_node *root_kn,
> > + struct kernfs_node *kn, char *buf,
> > + size_t buflen);
>
> I think I commented on the same thing before, but I think it'd make
> more sense to put @from after @to
Oh. You said that for kernfs_path_from_node_locked(), and those were
changed. kernfs_path_form_node() is a different fn, but
> and the prototype is using @root_kn
> which is a bit confusing.
we can rename kn_root to from here if you think that's clearer (and
change the order here as well).
> Was converting the path functions to return
> length too much work? If so, that's fine but please explain what
> decisions were made.
Yes, I had replied saying:
|I can change that, but the callers right now don't re-try with
|larger buffer anyway, so this would actually complicate them just
|a smidgeon. Would you want them changed to do that? (pr_cont_kernfs_path
|right now writes into a static char[] for instance)
I can still make that change if you like.
> I skimmed through the series and spotted several other review points
> which didn't get addressed. Can you please go over the previous
> review cycle and address the review points?
I did go through every email twice, once while making changes (one
branch per response) and once while making changelog for each patch,
sorry about whatever I missed. I'll go through each again.
I'm going to be out for awhile after today, so next version will
unfortunately take awhile.
thanks,
-serge
Hey,
On Wed, Dec 09, 2015 at 10:13:27PM +0000, Serge Hallyn wrote:
> we can rename kn_root to from here if you think that's clearer (and
> change the order here as well).
I think it'd be better for them to be consistent and in the same order
- the target and then the optional base.
> > Was converting the path functions to return
> > length too much work? If so, that's fine but please explain what
> > decisions were made.
>
> Yes, I had replied saying:
>
> |I can change that, but the callers right now don't re-try with
> |larger buffer anyway, so this would actually complicate them just
> |a smidgeon. Would you want them changed to do that? (pr_cont_kernfs_path
> |right now writes into a static char[] for instance)
>
> I can still make that change if you like.
Oops, sorry I forgot about that. The reason why kernfs_path() is
written the current way was me being lazy. While I think it'd be
better to make the functions behave like normal string handling
functions if we're extending it, I don't think it's that important.
If it's easy, please go ahead. If not, we can get back to it later
when necessary.
> > I skimmed through the series and spotted several other review points
> > which didn't get addressed. Can you please go over the previous
> > review cycle and address the review points?
>
> I did go through every email twice, once while making changes (one
> branch per response) and once while making changelog for each patch,
> sorry about whatever I missed. I'll go through each again.
The other chunk I noticed was inline conversions of internal functions
which didn't seem to belong to the patch. I asked whether those were
stray chunks. Maybe the comment was too buried to notice? Anyways,
that part actually causes conflicts when applying to cgroup/for-4.5.
There are a couple more things.
* Can you please put the ns related decls after the regular cgroup
stuff in cgroup.h?
* I think I might need to edit the documentation anyway but it'd be
great if you can make the namespace section more in line with the
rest of the documentation - e.g. s/CGroup/cgroup/ and more
structured sectioning.
At this point, it all generally looks good to me. Let's get the
nits out of the way and merge it.
Thanks.
--
tejun
On Wed, Dec 09, 2015 at 05:36:51PM -0500, Tejun Heo wrote:
> Hey,
>
> On Wed, Dec 09, 2015 at 10:13:27PM +0000, Serge Hallyn wrote:
> > we can rename kn_root to from here if you think that's clearer (and
> > change the order here as well).
>
> I think it'd be better for them to be consistent and in the same order
> - the target and then the optional base.
>
> > > Was converting the path functions to return
> > > length too much work? If so, that's fine but please explain what
> > > decisions were made.
> >
> > Yes, I had replied saying:
> >
> > |I can change that, but the callers right now don't re-try with
> > |larger buffer anyway, so this would actually complicate them just
> > |a smidgeon. Would you want them changed to do that? (pr_cont_kernfs_path
> > |right now writes into a static char[] for instance)
> >
> > I can still make that change if you like.
>
> Oops, sorry I forgot about that. The reason why kernfs_path() is
> written the current way was me being lazy. While I think it'd be
> better to make the functions behave like normal string handling
> functions if we're extending it, I don't think it's that important.
> If it's easy, please go ahead. If not, we can get back to it later
> when necessary.
Ok - I'm now gone until Dec 21 (and laptopping won't be an option :( ).
I'll make the other changes then and do this as well. So
pr_cont_kernfs_path() will dynamically allocate a longer buffer (only)
if needed.
> > > I skimmed through the series and spotted several other review points
> > > which didn't get addressed. Can you please go over the previous
> > > review cycle and address the review points?
> >
> > I did go through every email twice, once while making changes (one
> > branch per response) and once while making changelog for each patch,
> > sorry about whatever I missed. I'll go through each again.
>
> The other chunk I noticed was inline conversions of internal functions
> which didn't seem to belong to the patch. I asked whether those were
> stray chunks. Maybe the comment was too buried to notice? Anyways,
> that part actually causes conflicts when applying to cgroup/for-4.5.
Gah. I saw one and removed it. Grep tells me I missed some, will
remove them all next time.
> There are a couple more things.
>
> * Can you please put the ns related decls after the regular cgroup
> stuff in cgroup.h?
ok
> * I think I might need to edit the documentation anyway but it'd be
> great if you can make the namespace section more in line with the
> rest of the documentation - e.g. s/CGroup/cgroup/ and more
> structured sectioning.
I'll read through it and look for patterns to change.
> At this point, it all generally looks good to me. Let's get the
> nits out of the way and merge it.
>
> Thanks.
thanks,
-serge
On Wed, Dec 09, 2015 at 05:36:51PM -0500, Tejun Heo wrote:
> Hey,
>
> On Wed, Dec 09, 2015 at 10:13:27PM +0000, Serge Hallyn wrote:
> > we can rename kn_root to from here if you think that's clearer (and
> > change the order here as well).
>
> I think it'd be better for them to be consistent and in the same order
> - the target and then the optional base.
>
> > > Was converting the path functions to return
> > > length too much work? If so, that's fine but please explain what
> > > decisions were made.
> >
> > Yes, I had replied saying:
> >
> > |I can change that, but the callers right now don't re-try with
> > |larger buffer anyway, so this would actually complicate them just
> > |a smidgeon. Would you want them changed to do that? (pr_cont_kernfs_path
> > |right now writes into a static char[] for instance)
> >
> > I can still make that change if you like.
>
> Oops, sorry I forgot about that. The reason why kernfs_path() is
> written the current way was me being lazy. While I think it'd be
> better to make the functions behave like normal string handling
> functions if we're extending it, I don't think it's that important.
> If it's easy, please go ahead. If not, we can get back to it later
> when necessary.
>
> > > I skimmed through the series and spotted several other review points
> > > which didn't get addressed. Can you please go over the previous
> > > review cycle and address the review points?
> >
> > I did go through every email twice, once while making changes (one
> > branch per response) and once while making changelog for each patch,
> > sorry about whatever I missed. I'll go through each again.
>
> The other chunk I noticed was inline conversions of internal functions
> which didn't seem to belong to the patch. I asked whether those were
> stray chunks. Maybe the comment was too buried to notice? Anyways,
> that part actually causes conflicts when applying to cgroup/for-4.5.
>
> There are a couple more things.
>
> * Can you please put the ns related decls after the regular cgroup
> stuff in cgroup.h?
>
> * I think I might need to edit the documentation anyway but it'd be
> great if you can make the namespace section more in line with the
> rest of the documentation - e.g. s/CGroup/cgroup/ and more
> structured sectioning.
Ok fwiw I've fixed up the arguments to kernfs_path_from_node, removed
the inlines, and moved the ns related decls after the others in cgroup.h
(i.e. done the easy stuff) in the 2015-12-09/cgroupns.3 branch of
git://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux-security.git
I'll address the rest either after next week or, hopefully, when I get
a chance earlier.
> At this point, it all generally looks good to me. Let's get the
> nits out of the way and merge it.
If you wanted to take the branch as is, then I'll do the documentation
and pr_cont_kernfs_path() etc rewrite as separate patches, but I'll
assume you'd like to at least wait for doc rewrite.
-serge