netdev - [PATCH 3/3] x25: Prevent skb overreads when checking call user data

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Message-Id: <1318653905-13716-4-git-send-email-mattjd@gmail.com>
Date:	Sat, 15 Oct 2011 00:45:05 -0400
From:	Matthew Daley <mattjd@...il.com>
To:	netdev@...r.kernel.org
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Andrew Hendry <andrew.hendry@...il.com>,
	Matthew Daley <mattjd@...il.com>, stable <stable@...nel.org>
Subject: [PATCH 3/3] x25: Prevent skb overreads when checking call user data

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>
Cc: stable <stable@...nel.org>
---
 net/x25/af_x25.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index aa567b0..5f03e4e 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -295,7 +295,8 @@ static struct sock *x25_find_listener(struct x25_address *addr,
 			 * 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) {
-- 
1.7.2.5

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