qemu security update

CentOS Errata and Security Advisory CESA-2015:0867

KVM (Kernel-based Virtual Machine) 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. (CVE-2014-8106)

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. (BZ#1142756)

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.

Merged security bulletin from advisories:
https://lists.centos.org/pipermail/centos-announce/2015-April/083244.html

Affected packages:
qemu-guest-agent
qemu-img
qemu-kvm
qemu-kvm-tools

Upstream details at:
https://access.redhat.com/errata/RHSA-2015:0867