linux-kernel - [10/17] SCSI: aacraid: Eliminate use after free

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Date:	Fri, 30 Jul 2010 09:57:26 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Julia Lawall <julia@...u.dk>,
	James Bottomley <James.Bottomley@...e.de>
Subject: [10/17] SCSI: aacraid: Eliminate use after free

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Julia Lawall <julia@...u.dk>

commit 8a52da632ceb9d8b776494563df579e87b7b586b upstream.

The debugging code using the freed structure is moved before the kfree.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@free@
expression E;
position p;
@@
kfree@p(E)

@@
expression free.E, subE<=free.E, E1;
position free.p;
@@

  kfree@p(E)
  ...
(
  subE = E1
|
* E
)
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>
Signed-off-by: James Bottomley <James.Bottomley@...e.de>

---
 drivers/scsi/aacraid/commctrl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/scsi/aacraid/commctrl.c
+++ b/drivers/scsi/aacraid/commctrl.c
@@ -645,9 +645,9 @@ static int aac_send_raw_srb(struct aac_d
 				/* Does this really need to be GFP_DMA? */
 				p = kmalloc(usg->sg[i].count,GFP_KERNEL|__GFP_DMA);
 				if(!p) {
-					kfree (usg);
-					dprintk((KERN_DEBUG"aacraid: Could not allocate SG buffer - size = %d buffer number %d of %d\n",
+					dprintk((KERN_DEBUG "aacraid: Could not allocate SG buffer - size = %d buffer number %d of %d\n",
 					  usg->sg[i].count,i,usg->count));
+					kfree(usg);
 					rcode = -ENOMEM;
 					goto cleanup;
 				}


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