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memcg, slab: RCU protect memcg_params for root caches

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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>
This commit is contained in:
Vladimir Davydov
2014-01-23 15:53:06 -08:00
committed by Linus Torvalds
parent f717eb3abb
commit f8570263ee
3 changed files with 30 additions and 10 deletions
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15
mm/memcontrol.c
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@ -3178,18 +3178,17 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
if (num_groups > memcg_limited_groups_array_size) {
int i;
struct memcg_cache_params *new_params;
ssize_t size = memcg_caches_array_size(num_groups);
size *= sizeof(void *);
size += offsetof(struct memcg_cache_params, memcg_caches);
s->memcg_params = kzalloc(size, GFP_KERNEL);
if (!s->memcg_params) {
s->memcg_params = cur_params;
new_params = kzalloc(size, GFP_KERNEL);
if (!new_params)
return -ENOMEM;
}
s->memcg_params->is_root_cache = true;
new_params->is_root_cache = true;
/*
* There is the chance it will be bigger than
@ -3203,7 +3202,7 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
for (i = 0; i < memcg_limited_groups_array_size; i++) {
if (!cur_params->memcg_caches[i])
continue;
s->memcg_params->memcg_caches[i] =
new_params->memcg_caches[i] =
cur_params->memcg_caches[i];
}
@ -3216,7 +3215,9 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
* bigger than the others. And all updates will reset this
* anyway.
*/
kfree(cur_params);
rcu_assign_pointer(s->memcg_params, new_params);
if (cur_params)
kfree_rcu(cur_params, rcu_head);
}
return 0;
}