linux-kernel - [PATCH] memcg: avoid accessing memcg after releasing reference

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Message-ID: <5158F344.9020509@huawei.com>
Date:	Mon, 1 Apr 2013 10:39:00 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Glauber Costa <glommer@...allels.com>
CC:	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] memcg: avoid accessing memcg after releasing reference

This might cause use-after-free bug.

Signed-off-by: Li Zefan <lizefan@...wei.com>
---

found when reading the code.

---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8ec501c..6391046 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3186,12 +3186,12 @@ void memcg_release_cache(struct kmem_cache *s)
 
 	root = s->memcg_params->root_cache;
 	root->memcg_params->memcg_caches[id] = NULL;
-	mem_cgroup_put(memcg);
 
 	mutex_lock(&memcg->slab_caches_mutex);
 	list_del(&s->memcg_params->list);
 	mutex_unlock(&memcg->slab_caches_mutex);
 
+	mem_cgroup_put(memcg);
 out:
 	kfree(s->memcg_params);
 }
-- 
1.8.0.2
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