diff options
| author | Vladimir Davydov | 2014-01-23 15:53:06 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2014-01-23 16:36:51 -0800 |
| commit | f8570263ee16eb1d5038b8e20d7db3a68bbb2b49 (patch) | |
| tree | 06d54d7f5f357622604d1e8338478b906729409d /mm/slab.h | |
| parent | f717eb3abb5ea38f60e671dbfdbf512c2c93d22e (diff) | |
memcg, slab: RCU protect memcg_params for root caches
We relocate root cache's memcg_params whenever we need to grow the
memcg_caches array to accommodate all kmem-active memory cgroups.
Currently on relocation we free the old version immediately, which can
lead to use-after-free, because the memcg_caches array is accessed
lock-free (see cache_from_memcg_idx()). This patch fixes this by making
memcg_params RCU-protected for root caches.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab.h')
| -rw-r--r-- | mm/slab.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/mm/slab.h b/mm/slab.h index 72d1f9df71bd..8184a7cde272 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -160,14 +160,28 @@ static inline const char *cache_name(struct kmem_cache *s) return s->name; } +/* + * Note, we protect with RCU only the memcg_caches array, not per-memcg caches. + * That said the caller must assure the memcg's cache won't go away. Since once + * created a memcg's cache is destroyed only along with the root cache, it is + * true if we are going to allocate from the cache or hold a reference to the + * root cache by other means. Otherwise, we should hold either the slab_mutex + * or the memcg's slab_caches_mutex while calling this function and accessing + * the returned value. + */ static inline struct kmem_cache * cache_from_memcg_idx(struct kmem_cache *s, int idx) { struct kmem_cache *cachep; + struct memcg_cache_params *params; if (!s->memcg_params) return NULL; - cachep = s->memcg_params->memcg_caches[idx]; + + rcu_read_lock(); + params = rcu_dereference(s->memcg_params); + cachep = params->memcg_caches[idx]; + rcu_read_unlock(); /* * Make sure we will access the up-to-date value. The code updating |