net: ipv6: reset daddr and dport in sk if connect() fails

In __ip6_datagram_connect(), reset sk->sk_v6_daddr and inet->dport if
error occurs.
In udp_v6_early_demux(), check for sk_state to make sure it is in
TCP_ESTABLISHED state.
Together, it makes sure unconnected UDP socket won't be considered as a
valid candidate for early demux.

v3: add TCP_ESTABLISHED state check in udp_v6_early_demux()
v2: fix compilation error

Fixes: 5425077 ("net: ipv6: Add early demux handler for UDP unicast")
Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/datagram.c

@@ -250,8 +250,14 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
 	 */
 
 	err = ip6_datagram_dst_update(sk, true);
-	if (err)
+	if (err) {
+		/* Reset daddr and dport so that udp_v6_early_demux()
+		 * fails to find this socket
+		 */
+		memset(&sk->sk_v6_daddr, 0, sizeof(sk->sk_v6_daddr));
+		inet->inet_dport = 0;
 		goto out;
+	}
 
 	sk->sk_state = TCP_ESTABLISHED;
 	sk_set_txhash(sk);

net/ipv6/udp.c

@@ -879,7 +879,8 @@ static struct sock *__udp6_lib_demux_lookup(struct net *net,
 	struct sock *sk;
 
 	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
-		if (INET6_MATCH(sk, net, rmt_addr, loc_addr, ports, dif))
+		if (sk->sk_state == TCP_ESTABLISHED &&
+		    INET6_MATCH(sk, net, rmt_addr, loc_addr, ports, dif))
 			return sk;
 		/* Only check first socket in chain */
 		break;