Published: 25 November 2011
The kvm_vm_ioctl_assign_device function in virt/kvm/assigned-dev.c in the KVM subsystem in the Linux kernel before 3.1.10 does not verify permission to access PCI configuration space and BAR resources, which allows host OS users to assign PCI devices and cause a denial of service (host OS crash) via a KVM_ASSIGN_PCI_DEVICE operation. 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.
From the Ubuntu security team
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.