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authorLi Zefan <lizefan@huawei.com>2014-09-04 14:43:38 +0800
committerTejun Heo <tj@kernel.org>2014-09-05 01:36:19 +0900
commitaa32362f011c6e863132b16c1761487166a4bad2 (patch)
tree21274b6b6111e83af93568c4e7c10357f4e58a0f
parenta4189487da1b4f8260c6006b9dc47c3c4107a5ae (diff)
downloadlinux-next-aa32362f011c6e863132b16c1761487166a4bad2.tar.gz
cgroup: check cgroup liveliness before unbreaking kernfs
When cgroup_kn_lock_live() is called through some kernfs operation and another thread is calling cgroup_rmdir(), we'll trigger the warning in cgroup_get(). ------------[ cut here ]------------ WARNING: CPU: 1 PID: 1228 at kernel/cgroup.c:1034 cgroup_get+0x89/0xa0() ... Call Trace: [<c16ee73d>] dump_stack+0x41/0x52 [<c10468ef>] warn_slowpath_common+0x7f/0xa0 [<c104692d>] warn_slowpath_null+0x1d/0x20 [<c10bb999>] cgroup_get+0x89/0xa0 [<c10bbe58>] cgroup_kn_lock_live+0x28/0x70 [<c10be3c1>] __cgroup_procs_write.isra.26+0x51/0x230 [<c10be5b2>] cgroup_tasks_write+0x12/0x20 [<c10bb7b0>] cgroup_file_write+0x40/0x130 [<c11aee71>] kernfs_fop_write+0xd1/0x160 [<c1148e58>] vfs_write+0x98/0x1e0 [<c114934d>] SyS_write+0x4d/0xa0 [<c16f656b>] sysenter_do_call+0x12/0x12 ---[ end trace 6f2e0c38c2108a74 ]--- Fix this by calling css_tryget() instead of cgroup_get(). v2: - move cgroup_tryget() right below cgroup_get() definition. (Tejun) Cc: <stable@vger.kernel.org> # 3.15+ Reported-by: Toralf Förster <toralf.foerster@gmx.de> Signed-off-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/cgroup.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index bf30076664ca..940aced4ed00 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1035,6 +1035,11 @@ static void cgroup_get(struct cgroup *cgrp)
css_get(&cgrp->self);
}
+static bool cgroup_tryget(struct cgroup *cgrp)
+{
+ return css_tryget(&cgrp->self);
+}
+
static void cgroup_put(struct cgroup *cgrp)
{
css_put(&cgrp->self);
@@ -1147,7 +1152,8 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
* protection against removal. Ensure @cgrp stays accessible and
* break the active_ref protection.
*/
- cgroup_get(cgrp);
+ if (!cgroup_tryget(cgrp))
+ return NULL;
kernfs_break_active_protection(kn);
mutex_lock(&cgroup_mutex);