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

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Message-ID: <20121225185155.GE5318@thunk.org>
Date:	Tue, 25 Dec 2012 13:51:55 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	jack@...e.cz, akpm@...ux-foundation.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] fs/ext3: set pointer = NULL, after kfree it

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
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