memcg: fix possible NULL deref while traversing memcg_slab_caches list
All caches of the same memory cgroup are linked in the memcg_slab_caches list via kmem_cache::memcg_params::list. This list is traversed, for example, when we read memory.kmem.slabinfo. Since the list actually consists of memcg_cache_params objects, we have to convert an element of the list to a kmem_cache object using memcg_params_to_cache(), which obtains the pointer to the cache from the memcg_params::memcg_caches array of the corresponding root cache. That said the pointer to a kmem_cache in its parent's memcg_params must be initialized before adding the cache to the list, and cleared only after it has been unlinked. Currently it is vice-versa, which can result in a NULL ptr dereference while traversing the memcg_slab_caches list. This patch restores the correct order. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
959c8963fc
commit
96403da244
|
@ -3270,9 +3270,6 @@ void memcg_register_cache(struct kmem_cache *s)
|
||||||
|
|
||||||
css_get(&memcg->css);
|
css_get(&memcg->css);
|
||||||
|
|
||||||
mutex_lock(&memcg->slab_caches_mutex);
|
|
||||||
list_add(&s->memcg_params->list, &memcg->memcg_slab_caches);
|
|
||||||
mutex_unlock(&memcg->slab_caches_mutex);
|
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* Since readers won't lock (see cache_from_memcg_idx()), we need a
|
* Since readers won't lock (see cache_from_memcg_idx()), we need a
|
||||||
|
@ -3281,7 +3278,16 @@ void memcg_register_cache(struct kmem_cache *s)
|
||||||
*/
|
*/
|
||||||
smp_wmb();
|
smp_wmb();
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Initialize the pointer to this cache in its parent's memcg_params
|
||||||
|
* before adding it to the memcg_slab_caches list, otherwise we can
|
||||||
|
* fail to convert memcg_params_to_cache() while traversing the list.
|
||||||
|
*/
|
||||||
root->memcg_params->memcg_caches[id] = s;
|
root->memcg_params->memcg_caches[id] = s;
|
||||||
|
|
||||||
|
mutex_lock(&memcg->slab_caches_mutex);
|
||||||
|
list_add(&s->memcg_params->list, &memcg->memcg_slab_caches);
|
||||||
|
mutex_unlock(&memcg->slab_caches_mutex);
|
||||||
}
|
}
|
||||||
|
|
||||||
void memcg_unregister_cache(struct kmem_cache *s)
|
void memcg_unregister_cache(struct kmem_cache *s)
|
||||||
|
@ -3293,16 +3299,21 @@ void memcg_unregister_cache(struct kmem_cache *s)
|
||||||
if (is_root_cache(s))
|
if (is_root_cache(s))
|
||||||
return;
|
return;
|
||||||
|
|
||||||
memcg = s->memcg_params->memcg;
|
|
||||||
id = memcg_cache_id(memcg);
|
|
||||||
|
|
||||||
root = s->memcg_params->root_cache;
|
root = s->memcg_params->root_cache;
|
||||||
root->memcg_params->memcg_caches[id] = NULL;
|
memcg = s->memcg_params->memcg;
|
||||||
|
id = memcg_cache_id(memcg);
|
||||||
|
|
||||||
mutex_lock(&memcg->slab_caches_mutex);
|
mutex_lock(&memcg->slab_caches_mutex);
|
||||||
list_del(&s->memcg_params->list);
|
list_del(&s->memcg_params->list);
|
||||||
mutex_unlock(&memcg->slab_caches_mutex);
|
mutex_unlock(&memcg->slab_caches_mutex);
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Clear the pointer to this cache in its parent's memcg_params only
|
||||||
|
* after removing it from the memcg_slab_caches list, otherwise we can
|
||||||
|
* fail to convert memcg_params_to_cache() while traversing the list.
|
||||||
|
*/
|
||||||
|
root->memcg_params->memcg_caches[id] = NULL;
|
||||||
|
|
||||||
css_put(&memcg->css);
|
css_put(&memcg->css);
|
||||||
}
|
}
|
||||||
|
|
||||||
|
|
Loading…
Reference in New Issue