tipc: add a bounds check in link_recv_changeover_msg()

The bearer_id here comes from skb->data and it can be a number from 0 to
7.  The problem is that the ->links[] array has only 2 elements so I
have added a range check.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -2306,8 +2306,11 @@ static int link_recv_changeover_msg(struct tipc_link **l_ptr,
 	struct tipc_msg *tunnel_msg = buf_msg(tunnel_buf);
 	u32 msg_typ = msg_type(tunnel_msg);
 	u32 msg_count = msg_msgcnt(tunnel_msg);
+	u32 bearer_id = msg_bearer_id(tunnel_msg);
 
-	dest_link = (*l_ptr)->owner->links[msg_bearer_id(tunnel_msg)];
+	if (bearer_id >= MAX_BEARERS)
+		goto exit;
+	dest_link = (*l_ptr)->owner->links[bearer_id];
 	if (!dest_link)
 		goto exit;
 	if (dest_link == *l_ptr) {