From 051dd46050f2a9bdfff8cc067f8987069eae1743 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@parallels.com>
Date: Mon, 7 Apr 2014 15:39:27 -0700
Subject: [PATCH] memcg, slab: unregister cache from memcg before starting to
 destroy it

Currently, memcg_unregister_cache(), which deletes the cache being
destroyed from the memcg_slab_caches list, is called after
__kmem_cache_shutdown() (see kmem_cache_destroy()), which starts to
destroy the cache.

As a result, one can access a partially destroyed cache while traversing
a memcg_slab_caches list, which can have deadly consequences (for
instance, cache_show() called for each cache on a memcg_slab_caches list
from mem_cgroup_slabinfo_read() will dereference pointers to already
freed data).

To fix this, let's move memcg_unregister_cache() before the cache
destruction process beginning, issuing memcg_register_cache() on failure.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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