cgroups: use task_lock() for access tsk->cgroups safe in cgroup_clone()

Use task_lock() protect tsk->cgroups and get_css_set(tsk->cgroups).

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a288da176e46..00d5136d38c2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2903,6 +2903,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
                 mutex_unlock(&cgroup_mutex);
                 return 0;
         }
+        task_lock(tsk);
         cg = tsk->cgroups;
         parent = task_cgroup(tsk, subsys->subsys_id);
 
@@ -2915,6 +2916,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
 
         /* Keep the cgroup alive */
         get_css_set(cg);
+        task_unlock(tsk);
         mutex_unlock(&cgroup_mutex);
 
         /* Now do the VFS work to create a cgroup */