[049/107] x25: Prevent skb overreads when checking call user data

[Greg KH]

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

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

From: Matthew Daley <mattjd@xxxxxxxxx>

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@xxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Andrew Hendry <andrew.hendry@xxxxxxxxx>
Acked-by: Andrew Hendry <andrew.hendry@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 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
@@ -294,7 +294,8 @@ 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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