linux-kernel - Re: [PATCH 2/2] zram: avoid NULL pointer access when reading mem_used

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Message-ID: <20141026014450.GB3328@gmail.com>
Date:	Sun, 26 Oct 2014 10:44:50 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Weijie Yang <weijie.yang@...sung.com>
Cc:	'Andrew Morton' <akpm@...ux-foundation.org>,
	'Dan Streetman' <ddstreet@...e.org>,
	'Sergey Senozhatsky' <sergey.senozhatsky@...il.com>,
	'Nitin Gupta' <ngupta@...are.org>,
	'Linux-MM' <linux-mm@...ck.org>,
	'linux-kernel' <linux-kernel@...r.kernel.org>,
	'Weijie Yang' <weijie.yang.kh@...il.com>
Subject: Re: [PATCH 2/2] zram: avoid NULL pointer access when reading
 mem_used_total

On Sat, Oct 25, 2014 at 05:26:31PM +0800, Weijie Yang wrote:
> There is a rare NULL pointer bug in mem_used_total_show() in concurrent
> situation, like this:
> zram is not initialized, process A is a mem_used_total reader which runs
> periodicity, while process B try to init zram.
> 
> 	process A 				process B
> access meta, get a NULL value
> 						init zram, done
> init_done() is true
> access meta->mem_pool, get a NULL pointer BUG
> 
> This patch fixes this issue.
> 	
> Signed-off-by: Weijie Yang <weijie.yang@...sung.com>
Acked-by: Minchan Kim <minchan@...nel.org>

Thanks!

-- 
Kind regards,
Minchan Kim
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