linux-kernel - [24/27] x25: Prevent skb overreads when checking call user data

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Date:	Sun, 23 Oct 2011 08:24:52 +0200
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	stable-review@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Matthew Daley <mattjd@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Andrew Hendry <andrew.hendry@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [24/27] x25: Prevent skb overreads when checking call user data

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

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

From: Matthew Daley <mattjd@...il.com>

commit 7f81e25befdfb3272345a2e775f520e1d515fa20 upstream.

x25_find_listener does not check that the amount of call user data given
in the skb is big enough in per-socket comparisons, hence buffer
overreads may occur.  Fix this by adding a check.

Signed-off-by: Matthew Daley <mattjd@...il.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Andrew Hendry <andrew.hendry@...il.com>
Acked-by: Andrew Hendry <andrew.hendry@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/x25/af_x25.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -295,7 +295,8 @@ static struct sock *x25_find_listener(st
 			 * Found a listening socket, now check the incoming
 			 * call user data vs this sockets call user data
 			 */
-			if(skb->len > 0 && x25_sk(s)->cudmatchlength > 0) {
+			if (x25_sk(s)->cudmatchlength > 0 &&
+				skb->len >= x25_sk(s)->cudmatchlength) {
 				if((memcmp(x25_sk(s)->calluserdata.cuddata,
 					skb->data,
 					x25_sk(s)->cudmatchlength)) == 0) {


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