iucv: Fix missing msg_namelen update in iucv_sock_recvmsg()

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 iucv_sock_recvmsg() not filling the msg_name in case it was set.

Cc: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static void iucv_callback_connrej(struct iucv_path *path, u8 ipuser[16])
{
	struct sock *sk = path->private;

	if (sk->sk_state == IUCV_CLOSED)
		return;

	bh_lock_sock(sk);
	iucv_sever_path(sk, 1);
	sk->sk_state = IUCV_DISCONN;

	sk->sk_state_change(sk);
	bh_unlock_sock(sk);
}

static void iucv_callback_connrej(struct iucv_path *path, u8 ipuser[16])
{
	struct sock *sk = path->private;

	if (sk->sk_state == IUCV_CLOSED)
		return;

	bh_lock_sock(sk);
	iucv_sever_path(sk, 1);
	sk->sk_state = IUCV_DISCONN;

	sk->sk_state_change(sk);
	bh_unlock_sock(sk);
}
