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authorLi Zefan <lizefan@huawei.com>2014-02-11 16:05:46 +0800
committerTejun Heo <tj@kernel.org>2014-02-11 10:38:30 -0500
commit0ab02ca8f887908152d1a96db5130fc661d36a1e (patch)
tree81f7be1f4da646a88ab09bd7c01927a4f2a180bf /include/linux
parent48573a893303986e3b0b2974d6fb11f3d1bb7064 (diff)
cgroup: protect modifications to cgroup_idr with cgroup_mutex
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}(). tj: Refreshed on top of b58c89986a77 ("cgroup: fix error return from cgroup_create()"). 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: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/cgroup.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 5c097596104b..9450f025fe0c 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -166,6 +166,8 @@ 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;

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