linux-kernel - Re: [PATCH] memcg: avoid accessing memcg after releasing reference

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Message-ID: <20130401093927.GB30749@dhcp22.suse.cz>
Date:	Mon, 1 Apr 2013 11:39:27 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Glauber Costa <glommer@...allels.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] memcg: avoid accessing memcg after releasing reference

On Mon 01-04-13 10:39:00, Li Zefan wrote:
> This might cause use-after-free bug.
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>

Acked-by: Michal Hocko <mhocko@...e.cz>

> ---
> 
> found when reading the code.
> 
> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8ec501c..6391046 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3186,12 +3186,12 @@ void memcg_release_cache(struct kmem_cache *s)
>  
>  	root = s->memcg_params->root_cache;
>  	root->memcg_params->memcg_caches[id] = NULL;
> -	mem_cgroup_put(memcg);
>  
>  	mutex_lock(&memcg->slab_caches_mutex);
>  	list_del(&s->memcg_params->list);
>  	mutex_unlock(&memcg->slab_caches_mutex);
>  
> +	mem_cgroup_put(memcg);
>  out:
>  	kfree(s->memcg_params);
>  }
> -- 
> 1.8.0.2

-- 
Michal Hocko
SUSE Labs
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