diff options
| author | Li Zefan <lizefan@huawei.com> | 2014-02-11 16:05:46 +0800 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-03-26 12:24:36 +0100 |
| commit | 59d9c5f94655a3cc63e2772e847509010598b7f1 (patch) | |
| tree | 5e6bfcb084cbd950bf88ea5b96114f294acbfbc5 /include | |
| parent | 293639e5b70e7c19b36bf1504d09dac574b30895 (diff) | |
| download | lwn-59d9c5f94655a3cc63e2772e847509010598b7f1.tar.gz lwn-59d9c5f94655a3cc63e2772e847509010598b7f1.zip | |
cgroup: protect modifications to cgroup_idr with cgroup_mutex
commit 0ab02ca8f887908152d1a96db5130fc661d36a1e upstream.
Setup cgroupfs like this:
# mount -t cgroup -o cpuacct xxx /cgroup
# mkdir /cgroup/sub1
# mkdir /cgroup/sub2
Then run these two commands:
# for ((; ;)) { mkdir /cgroup/sub1/tmp && rmdir /mnt/sub1/tmp; } &
# for ((; ;)) { mkdir /cgroup/sub2/tmp && rmdir /mnt/sub2/tmp; } &
After seconds you may see this warning:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 25243 at lib/idr.c:527 sub_remove+0x87/0x1b0()
idr_remove called for id=6 which is not allocated.
...
Call Trace:
[<ffffffff8156063c>] dump_stack+0x7a/0x96
[<ffffffff810591ac>] warn_slowpath_common+0x8c/0xc0
[<ffffffff81059296>] warn_slowpath_fmt+0x46/0x50
[<ffffffff81300aa7>] sub_remove+0x87/0x1b0
[<ffffffff810f3f02>] ? css_killed_work_fn+0x32/0x1b0
[<ffffffff81300bf5>] idr_remove+0x25/0xd0
[<ffffffff810f2bab>] cgroup_destroy_css_killed+0x5b/0xc0
[<ffffffff810f4000>] css_killed_work_fn+0x130/0x1b0
[<ffffffff8107cdbc>] process_one_work+0x26c/0x550
[<ffffffff8107eefe>] worker_thread+0x12e/0x3b0
[<ffffffff81085f96>] kthread+0xe6/0xf0
[<ffffffff81570bac>] ret_from_fork+0x7c/0xb0
---[ end trace 2d1577ec10cf80d0 ]---
It's because allocating/removing cgroup ID is not properly synchronized.
The bug was introduced when we converted cgroup_ida to cgroup_idr.
While synchronization is already done inside ida_simple_{get,remove}(),
users are responsible for concurrent calls to idr_{alloc,remove}().
[mhocko@suse.cz: ported to 3.12]
Fixes: 4e96ee8e981b ("cgroup: convert cgroup_ida to cgroup_idr")
Cc: <stable@vger.kernel.org> #3.12+
Reported-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/cgroup.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 3561d305b1e0..7b3a119c51c2 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -169,6 +169,8 @@ struct cgroup { * * The ID of the root cgroup is always 0, and a new cgroup * will be assigned with a smallest available ID. + * + * Allocating/Removing ID must be protected by cgroup_mutex. */ int id; |