irda: Fix missing msg_namelen update in irda_recvmsg_dgram()

The current code does not fill the msg_name member in case it is set.
It also does not set the msg_namelen member to 0 and therefore makes
net/socket.c leak the local, uninitialized sockaddr_storage variable
to userland -- 128 bytes of kernel stack memory.

Fix that by simply setting msg_namelen to 0 as obviously nobody cared
about irda_recvmsg_dgram() not filling the msg_name in case it was
set.

Cc: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int irda_listen(struct socket *sock, int backlog)
{
	struct sock *sk = sock->sk;
	int err = -EOPNOTSUPP;

	IRDA_DEBUG(2, "%s()\n", __func__);

	lock_sock(sk);

	if ((sk->sk_type != SOCK_STREAM) && (sk->sk_type != SOCK_SEQPACKET) &&
	    (sk->sk_type != SOCK_DGRAM))
		goto out;

	if (sk->sk_state != TCP_LISTEN) {
		sk->sk_max_ack_backlog = backlog;
		sk->sk_state           = TCP_LISTEN;

		err = 0;
	}
out:
	release_sock(sk);

	return err;
}

static int irda_listen(struct socket *sock, int backlog)
{
	struct sock *sk = sock->sk;
	int err = -EOPNOTSUPP;

	IRDA_DEBUG(2, "%s()\n", __func__);

	lock_sock(sk);

	if ((sk->sk_type != SOCK_STREAM) && (sk->sk_type != SOCK_SEQPACKET) &&
	    (sk->sk_type != SOCK_DGRAM))
		goto out;

	if (sk->sk_state != TCP_LISTEN) {
		sk->sk_max_ack_backlog = backlog;
		sk->sk_state           = TCP_LISTEN;

		err = 0;
	}
out:
	release_sock(sk);

	return err;
}
