From f8570263ee16eb1d5038b8e20d7db3a68bbb2b49 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 23 Jan 2014 15:53:06 -0800 Subject: 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 Cc: Michal Hocko Cc: Glauber Costa Cc: Johannes Weiner Cc: Balbir Singh Cc: KAMEZAWA Hiroyuki Cc: Pekka Enberg Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/slab.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'include/linux/slab.h') diff --git a/include/linux/slab.h b/include/linux/slab.h index 1e2f4fe..a060142 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -513,7 +513,9 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) * * Both the root cache and the child caches will have it. For the root cache, * this will hold a dynamically allocated array large enough to hold - * information about the currently limited memcgs in the system. + * information about the currently limited memcgs in the system. To allow the + * array to be accessed without taking any locks, on relocation we free the old + * version only after a grace period. * * Child caches will hold extra metadata needed for its operation. Fields are: * @@ -528,7 +530,10 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) struct memcg_cache_params { bool is_root_cache; union { - struct kmem_cache *memcg_caches[0]; + struct { + struct rcu_head rcu_head; + struct kmem_cache *memcg_caches[0]; + }; struct { struct mem_cgroup *memcg; struct list_head list; -- cgit v1.1