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| author | Li Zefan <lizf@cn.fujitsu.com> | 2009-01-04 12:00:45 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-04 13:33:19 -0800 |
| commit | 7b574b7b0124ed344911f5d581e9bc2d83bbeb19 (patch) | |
| tree | 6511203310d77359017accb466f3f5e1e90abe13 /kernel/cgroup.c | |
| parent | 7d3b56ba37a95f1f370f50258ed3954c304c524b (diff) | |
| download | lwn-7b574b7b0124ed344911f5d581e9bc2d83bbeb19.tar.gz lwn-7b574b7b0124ed344911f5d581e9bc2d83bbeb19.zip | |
cgroups: fix a race between cgroup_clone and umount
The race is calling cgroup_clone() while umounting the ns cgroup subsys,
and thus cgroup_clone() might access invalid cgroup_fs, or kill_sb() is
called after cgroup_clone() created a new dir in it.
The BUG I triggered is BUG_ON(root->number_of_cgroups != 1);
------------[ cut here ]------------
kernel BUG at kernel/cgroup.c:1093!
invalid opcode: 0000 [#1] SMP
...
Process umount (pid: 5177, ti=e411e000 task=e40c4670 task.ti=e411e000)
...
Call Trace:
[<c0493df7>] ? deactivate_super+0x3f/0x51
[<c04a3600>] ? mntput_no_expire+0xb3/0xdd
[<c04a3ab2>] ? sys_umount+0x265/0x2ac
[<c04a3b06>] ? sys_oldumount+0xd/0xf
[<c0403911>] ? sysenter_do_call+0x12/0x31
...
EIP: [<c0456e76>] cgroup_kill_sb+0x23/0xe0 SS:ESP 0068:e411ef2c
---[ end trace c766c1be3bf944ac ]---
Cc: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 48348dde6d81..891a84eb9d30 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2945,7 +2945,11 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys, parent = task_cgroup(tsk, subsys->subsys_id); /* Pin the hierarchy */ - atomic_inc(&parent->root->sb->s_active); + if (!atomic_inc_not_zero(&parent->root->sb->s_active)) { + /* We race with the final deactivate_super() */ + mutex_unlock(&cgroup_mutex); + return 0; + } /* Keep the cgroup alive */ get_css_set(cg); |