mm: memcontrol: fix possible css ref leak on oom

mem_cgroup_oom may be invoked multiple times while a process is handling
a page fault, in which case current->memcg_in_oom will be overwritten
leaking the previously taken css reference.

Link: http://lkml.kernel.org/r/1464019330-7579-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b3f16ab4b4311d00efd34e9e53022a42b0d43d28..cf428d7b9a03a041516e613563d5d051dfc4c610 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1604,7 +1604,7 @@ static void memcg_oom_recover(struct mem_cgroup *memcg)
 
 static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
 {
-       if (!current->memcg_may_oom)
+       if (!current->memcg_may_oom || current->memcg_in_oom)
                return;
        /*
         * We are in the middle of the charge context here, so we