linux-kernel - Re: [ 05/11] ext4: fix memory leak in xattr

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Date:	Mon, 21 Oct 2013 12:37:32 -0400
From:	Dave Jones <davej@...hat.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Dave Jones <davej@...oraproject.org>,
	Theodore Tso <tytso@....edu>, Eric Sandeen <sandeen@...hat.com>
Subject: Re: [ 05/11] ext4: fix memory leak in xattr

On Fri, Oct 18, 2013 at 12:53:34PM -0700, Greg Kroah-Hartman wrote:
 > 3.4-stable review patch.  If anyone has any objections, please let me know.
 > 
 > ------------------
 > 
 > From: Dave Jones <davej@...hat.com>
 > 
 > commit 6e4ea8e33b2057b85d75175dd89b93f5e26de3bc upstream.
 > 
 > If we take the 2nd retry path in ext4_expand_extra_isize_ea, we
 > potentionally return from the function without having freed these
 > allocations.  If we don't do the return, we over-write the previous
 > allocation pointers, so we leak either way.
 > 
 > Spotted with Coverity.
 > 
 > [ Fixed by tytso to set is and bs to NULL after freeing these
 >   pointers, in case in the retry loop we later end up triggering an
 >   error causing a jump to cleanup, at which point we could have a double
 >   free bug. -- Ted ]
 > 
 > Signed-off-by: Dave Jones <davej@...oraproject.org>
 > Signed-off-by: "Theodore Ts'o" <tytso@....edu>
 > Reviewed-by: Eric Sandeen <sandeen@...hat.com>
 > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

I'm still waiting to hear if we also need this..

Ted ?

-- 

If we take the retry path here, we end up potentially overwriting bh, leaving
it with an elevated reference count.

Signed-off-by: Dave Jones <davej@...oraproject.org>

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 03e9beb..1423c48 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1352,6 +1352,7 @@ retry:
 					new_extra_isize = s_min_extra_isize;
 					kfree(is); is = NULL;
 					kfree(bs); bs = NULL;
+					brelse(bh);
 					goto retry;
 				}
 				error = -1;

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