KVM is a full virtualization solution for Linux on AMD64 and Intel 64 systems. The qemu-kvm package provides the user-space component for running virtual machines using KVM. It was found that the Cirrus blit region checks were insufficient. A privileged guest user could use this flaw to write outside of VRAM- allocated buffer boundaries in the host"s QEMU process address space with attacker-provided data. This issue was found by Paolo Bonzini of Red Hat. This update also fixes the following bug: * Previously, the effective downtime during the last phase of a live migration would sometimes be much higher than the maximum downtime specified by "migration_downtime" in vdsm.conf. This problem has been corrected. The value of "migration_downtime" is now honored and the migration is aborted if the downtime cannot be achieved. All qemu-kvm users are advised to upgrade to these updated packages, which contain a backported patch to correct this issue. After installing this update, shut down all running virtual machines. Once all virtual machines have shut down, start them again for this update to take effect.