From: Vladimir Davydov <vdavydov@virtuozzo.com>
Date: Mon, 23 May 2016 23:22:29 +0000 (-0700)
Subject: mm: memcontrol: fix possible css ref leak on oom
X-Git-Url: http://git.efficios.com/?a=commitdiff_plain;h=1383399d7be029281997889df23150fa6c16be6e;p=deliverable%2Flinux.git

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 b3f16ab4b431..cf428d7b9a03 100644
--- 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