net/af_iucv: drop inbound packets with invalid flags

Inbound packets may have any combination of flag bits set in their iucv
header. If we don't know how to handle a specific combination, drop the
skb instead of leaking it.

To clarify what error is returned in this case, replace the hard-coded
0 with the corresponding macro.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/iucv/af_iucv.c

@@ -2155,8 +2155,8 @@ static int afiucv_hs_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct sock *sk;
 	struct iucv_sock *iucv;
 	struct af_iucv_trans_hdr *trans_hdr;
+	int err = NET_RX_SUCCESS;
 	char nullstring[8];
-	int err = 0;
 
 	if (skb->len < (ETH_HLEN + sizeof(struct af_iucv_trans_hdr))) {
 		WARN_ONCE(1, "AF_IUCV too short skb, len=%d, min=%d",
@@ -2254,7 +2254,7 @@ static int afiucv_hs_rcv(struct sk_buff *skb, struct net_device *dev,
 		err = afiucv_hs_callback_rx(sk, skb);
 		break;
 	default:
-		;
+		kfree_skb(skb);
 	}
 
 	return err;