netns: Don't leak others' openreq-s in proc

The /proc/net/tcp leaks openreq sockets from other namespaces.
Signed-off-by: NPavel Emelyanov <xemul@parallels.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_ipv4.c

@@ -2043,7 +2043,9 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
 	}
 get_sk:
 	sk_nulls_for_each_from(sk, node) {
-		if (sk->sk_family == st->family && net_eq(sock_net(sk), net)) {
+		if (!net_eq(sock_net(sk), net))
+			continue;
+		if (sk->sk_family == st->family) {
 			cur = sk;
 			goto out;
 		}