linux-ext4 - Re: [PATCH] fs/ext3: set pointer = NULL, after kfree it

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Date:	Wed, 26 Dec 2012 10:33:12 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Theodore Ts'o <tytso@....edu>
CC:	jack@...e.cz, akpm@...ux-foundation.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] fs/ext3: set pointer = NULL, after kfree it

于 2012年12月26日 02:51, Theodore Ts'o 写道:
> On Mon, Dec 24, 2012 at 01:58:14PM +0800, Chen Gang wrote:
>>
>>   set s->base = NULL, after kfree it.
>>
>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
> 
> Was this to fix something flagged by some static code checker?  The
> only caller of ext3_xattr_block_set() is ext3_xattr_set_handle(), and
> s->base is stored on the stack, and as soon as ext3_xattr_block_set()
> returns, the object will disappear.  So it seems pretty hard to see
> how this could lead to a use-after-free bug.
> 
>     	       	       	 		- Ted
> 
> 

  this patch is not for a bug

  it is only for coding habit:
    it is better to set is to NULL, after kfree it.
    in the future, if another functions need call ext3_xattr_block_set, too.
      it will avoid another members to make mistake.

  since it is not for fixing bug, it is really a minor patch.
  I can understand if you do not apply it.

-- 
Chen Gang

Asianux Corporation
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