tipc: Reject payload messages with invalid message type

Adds check to ensure TIPC sockets reject incoming payload messages
that have an unrecognized message type.

Remove the old open question about whether TIPC_ERR_NO_PORT is
the proper return value.  It is appropriate here since there are
valid instances where another node can make use of the reply,
and at this point in time the host is already broadcasting TIPC
data, so there are no real security concerns.
Signed-off-by: NAllan Stephens <allan.stephens@windriver.com>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/socket.c

@@ -1223,11 +1223,8 @@ static u32 filter_rcv(struct sock *sk, struct sk_buff *buf)
 
 	/* Reject message if it is wrong sort of message for socket */
 
-	/*
-	 * WOULD IT BE BETTER TO JUST DISCARD THESE MESSAGES INSTEAD?
-	 * "NO PORT" ISN'T REALLY THE RIGHT ERROR CODE, AND THERE MAY
-	 * BE SECURITY IMPLICATIONS INHERENT IN REJECTING INVALID TRAFFIC
-	 */
+	if (msg_type(msg) > TIPC_DIRECT_MSG)
+		return TIPC_ERR_NO_PORT;
 
 	if (sock->state == SS_READY) {
 		if (msg_connected(msg))