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memcg, slab: unregister cache from memcg before starting to destroy it

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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>
This commit is contained in:
Vladimir Davydov 2014-04-07 15:39:27 -07:00 committed by Linus Torvalds
parent 794b1248be
commit 051dd46050
2 changed files with 8 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
mm/memcontrol.c
View file

@ -3140,6 +3140,7 @@ int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
s->memcg_params->root_cache = root_cache;
INIT_WORK(&s->memcg_params->destroy,
kmem_cache_destroy_work_func);
css_get(&memcg->css);
} else
s->memcg_params->is_root_cache = true;
@ -3148,6 +3149,10 @@ int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
void memcg_free_cache_params(struct kmem_cache *s)
{
if (!s->memcg_params)
return;
if (!s->memcg_params->is_root_cache)
css_put(&s->memcg_params->memcg->css);
kfree(s->memcg_params);
}
@ -3170,9 +3175,6 @@ void memcg_register_cache(struct kmem_cache *s)
memcg = s->memcg_params->memcg;
id = memcg_cache_id(memcg);
css_get(&memcg->css);
/*
* Since readers won't lock (see cache_from_memcg_idx()), we need a
* barrier here to ensure nobody will see the kmem_cache partially
@ -3221,10 +3223,8 @@ void memcg_unregister_cache(struct kmem_cache *s)
* after removing it from the memcg_slab_caches list, otherwise we can
* fail to convert memcg_params_to_cache() while traversing the list.
*/
VM_BUG_ON(!root->memcg_params->memcg_caches[id]);
VM_BUG_ON(root->memcg_params->memcg_caches[id] != s);
root->memcg_params->memcg_caches[id] = NULL;
css_put(&memcg->css);
}
/*

3
mm/slab_common.c
View file

@ -313,9 +313,9 @@ void kmem_cache_destroy(struct kmem_cache *s)
s->refcount--;
if (!s->refcount) {
list_del(&s->list);
memcg_unregister_cache(s);
if (!__kmem_cache_shutdown(s)) {
memcg_unregister_cache(s);
mutex_unlock(&slab_mutex);
if (s->flags & SLAB_DESTROY_BY_RCU)
rcu_barrier();
@ -325,6 +325,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
kmem_cache_free(kmem_cache, s);
} else {
list_add(&s->list, &slab_caches);
memcg_register_cache(s);
mutex_unlock(&slab_mutex);
printk(KERN_ERR "kmem_cache_destroy %s: Slab cache still has objects\n",
s->name);