It was found that kvm_vm_ioctl_assign_device function did not check if
the user requesting assignment was privileged or not. Together with
/dev/kvm being 666, unprivileged user could assign unused pci devices,
or even devices that were in use and whose resources were not properly
claimed by the respective drivers.
Please note that privileged access was still needed to re-program the
device to for example issue DMA requests. This is typically achieved by
touching files on sysfs filesystem. These files are usually not
accessible to unprivileged users.
As a result, local user could use this flaw to crash the system.

Sasha Levin discovered a flaw in the permission checking for device
assignments requested via the kvm ioctl in the Linux kernel. A local user
could use this flaw to crash the system causing a denial of service.