vfio/pci: Fix integer overflows, bitmask check

The VFIO_DEVICE_SET_IRQS ioctl did not sufficiently sanitize
user-supplied integers, potentially allowing memory corruption. This
patch adds appropriate integer overflow checks, checks the range bounds
for VFIO_IRQ_SET_DATA_NONE, and also verifies that only single element
in the VFIO_IRQ_SET_DATA_TYPE_MASK bitmask is set.
VFIO_IRQ_SET_ACTION_TYPE_MASK is already correctly checked later in
vfio_pci_set_irqs_ioctl().

Furthermore, a kzalloc is changed to a kcalloc because the use of a
kzalloc with an integer multiplication allowed an integer overflow
condition to be reached without this patch. kcalloc checks for overflow
and should prevent a similar occurrence.

Signed-off-by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
static int vfio_pci_open(void *device_data)
{
	struct vfio_pci_device *vdev = device_data;
	int ret = 0;

	if (!try_module_get(THIS_MODULE))
		return -ENODEV;

	mutex_lock(&driver_lock);

	if (!vdev->refcnt) {
		ret = vfio_pci_enable(vdev);
		if (ret)
			goto error;

		vfio_spapr_pci_eeh_open(vdev->pdev);
	}
	vdev->refcnt++;
error:
	mutex_unlock(&driver_lock);
	if (ret)
		module_put(THIS_MODULE);
	return ret;
}

static int vfio_pci_open(void *device_data)
{
	struct vfio_pci_device *vdev = device_data;
	int ret = 0;

	if (!try_module_get(THIS_MODULE))
		return -ENODEV;

	mutex_lock(&driver_lock);

	if (!vdev->refcnt) {
		ret = vfio_pci_enable(vdev);
		if (ret)
			goto error;

		vfio_spapr_pci_eeh_open(vdev->pdev);
	}
	vdev->refcnt++;
error:
	mutex_unlock(&driver_lock);
	if (ret)
		module_put(THIS_MODULE);
	return ret;
}
