x25: Prevent skb overreads when checking call user data

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@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Andrew Hendry <andrew.hendry@gmail.com>
Acked-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 04f83ab50edc7ed186b2a484dee46f41c547d945..32422a4a17c0b8908e4453c54677673bd078d3a5 100644 (file)
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -294,7 +294,8 @@ 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) {