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Commit e014e944 authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio: Protect vfio_dev_present against device_del 



vfio_dev_present is meant to give us a wait_event callback so that we
can block removing a device from vfio until it becomes unused.  The
root of this check depends on being able to get the iommu group from
the device.  Unfortunately if the BUS_NOTIFY_DEL_DEVICE notifier has
fired then the device-group reference is no longer searchable and we
fail the lookup.

We don't need to go to such extents for this though.  We have a
reference to the device, from which we can acquire a reference to the
group.  We can then use the group reference to search for the device
and properly block removal.

Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 906ee99d

drivers/vfio/vfio.c

+12 −21
Original line number Diff line number Diff line
@@ -642,33 +642,16 @@ int vfio_add_group_dev(struct device *dev, 
}

EXPORT_SYMBOL_GPL(vfio_add_group_dev);



/* Test whether a struct device is present in our tracking */

static bool vfio_dev_present(struct device *dev)

/* Given a referenced group, check if it contains the device */

static bool vfio_dev_present(struct vfio_group *group, struct device *dev)

{

	struct iommu_group *iommu_group;

	struct vfio_group *group;

	struct vfio_device *device;



	iommu_group = iommu_group_get(dev);

	if (!iommu_group)

		return false;



	group = vfio_group_get_from_iommu(iommu_group);

	if (!group) {

		iommu_group_put(iommu_group);

		return false;

	}



	device = vfio_group_get_device(group, dev);

	if (!device) {

		vfio_group_put(group);

		iommu_group_put(iommu_group);

	if (!device)

		return false;

	}



	vfio_device_put(device);

	vfio_group_put(group);

	iommu_group_put(iommu_group);

	return true;

}
@@ -682,10 +665,18 @@ void *vfio_del_group_dev(struct device *dev) 
	struct iommu_group *iommu_group = group->iommu_group;

	void *device_data = device->device_data;



	/*

	 * The group exists so long as we have a device reference.  Get

	 * a group reference and use it to scan for the device going away.

	 */

	vfio_group_get(group);



	vfio_device_put(device);



	/* TODO send a signal to encourage this to be released */

	wait_event(vfio.release_q, !vfio_dev_present(dev));

	wait_event(vfio.release_q, !vfio_dev_present(group, dev));



	vfio_group_put(group);



	iommu_group_put(iommu_group);