sock_diag: fetch source port from inet_sock

When an inet_sock is destroyed, its source port (sk_num) is set to
zero as part of the unhash procedure.  In order to supply a source
port as part of the NETLINK_SOCK_DIAG socket destruction broadcasts,
the source port number must be read from inet_sport instead.

Tested: ss -E
Signed-off-by: NCraig Gallek <kraig@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/inet_diag.c

@@ -1095,6 +1095,8 @@ int inet_diag_handler_get_info(struct sk_buff *skb, struct sock *sk)
 	r = nlmsg_data(nlh);
 	memset(r, 0, sizeof(*r));
 	inet_diag_msg_common_fill(r, sk);
+	if (sk->sk_type == SOCK_DGRAM || sk->sk_type == SOCK_STREAM)
+		r->id.idiag_sport = inet_sk(sk)->inet_sport;
 	r->idiag_state = sk->sk_state;
 
 	if ((err = nla_put_u8(skb, INET_DIAG_PROTOCOL, sk->sk_protocol))) {