memcontrol: rcu_read_lock() to protect mm_match_cgroup()

mm_match_cgroup() calls cgroup_subsys_state().

We must use rcu_read_lock() to protect cgroup_subsys_state().

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Reviewed-by: 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, 9 insertions, 2 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 472efd09118c..2de6504e01fb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -61,8 +61,15 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
 
 extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 
-#define mm_match_cgroup(mm, cgroup)     \
-        ((cgroup) == mem_cgroup_from_task((mm)->owner))
+static inline
+int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
+{
+        struct mem_cgroup *mem;
+        rcu_read_lock();
+        mem = mem_cgroup_from_task((mm)->owner);
+        rcu_read_unlock();
+        return cgroup == mem;
+}
 
 extern int
 mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr);