linux-kernel - Re: [patch] memcg: null dereference on allocation failure

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Message-ID: <20101028155207.GB3769@balbir.in.ibm.com>
Date:	Thu, 28 Oct 2010 21:22:07 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Dan Carpenter <error27@...il.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] memcg: null dereference on allocation failure

* Dan Carpenter <error27@...il.com> [2010-10-28 13:12:41]:

> The original code had a null dereference if alloc_percpu() failed.
> This was introduced in 711d3d2c9bc3 "memcg: cpu hotplug aware percpu
> count updates"
> 
> Signed-off-by: Dan Carpenter <error27@...il.com>
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9a99cfa..2efa8ea 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4208,15 +4208,17 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
> 
>  	memset(mem, 0, size);
>  	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
> -	if (!mem->stat) {
> -		if (size < PAGE_SIZE)
> -			kfree(mem);
> -		else
> -			vfree(mem);
> -		mem = NULL;
> -	}
> +	if (!mem->stat)
> +		goto out_free;
>  	spin_lock_init(&mem->pcp_counter_lock);
>  	return mem;
> +
> +out_free:
> +	if (size < PAGE_SIZE)
> +		kfree(mem);
> +	else
> +		vfree(mem);
> +	return NULL;
>  }

Good catch!
Reviewed-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
 

-- 
	Three Cheers,
	Balbir
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