unix_diag: fix info leak

When filling the netlink message we miss to wipe the pad field,
therefore leak one byte of heap memory to userland. Fix this by
setting pad to 0.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/unix/diag.c

@@ -124,6 +124,7 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 	rep->udiag_family = AF_UNIX;
 	rep->udiag_type = sk->sk_type;
 	rep->udiag_state = sk->sk_state;
+	rep->pad = 0;
 	rep->udiag_ino = sk_ino;
 	sock_diag_save_cookie(sk, rep->udiag_cookie);