VSOCK: Fix missing msg_namelen update in vsock_stream_recvmsg()

The code misses to update 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.

Cc: Andy King <acking@vmware.com>
Cc: Dmitry Torokhov <dtor@vmware.com>
Cc: George Zhang <georgezhang@vmware.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static long vsock_dev_do_ioctl(struct file *filp,
			       unsigned int cmd, void __user *ptr)
{
	u32 __user *p = ptr;
	int retval = 0;

	switch (cmd) {
	case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
		if (put_user(transport->get_local_cid(), p) != 0)
			retval = -EFAULT;
		break;

	default:
		pr_err("Unknown ioctl %d\n", cmd);
		retval = -EINVAL;
	}

	return retval;
}

static long vsock_dev_do_ioctl(struct file *filp,
			       unsigned int cmd, void __user *ptr)
{
	u32 __user *p = ptr;
	int retval = 0;

	switch (cmd) {
	case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
		if (put_user(transport->get_local_cid(), p) != 0)
			retval = -EFAULT;
		break;

	default:
		pr_err("Unknown ioctl %d\n", cmd);
		retval = -EINVAL;
	}

	return retval;
}
