From 051dd46050f2a9bdfff8cc067f8987069eae1743 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov 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 Cc: Michal Hocko Cc: Johannes Weiner Cc: David Rientjes Cc: Pekka Enberg Cc: Glauber Costa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 12 ++++++------ mm/slab_common.c | 3 ++- 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 451523c3bd4e..c22d8bf42d9a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -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); } /* diff --git a/mm/slab_common.c b/mm/slab_common.c index ccc012f00126..0c2879ff414c 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -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); -- 2.34.1