qemu security update

CentOS Errata and Security Advisory CESA-2013:0896

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component
for running virtual machines using KVM.

It was found that QEMU Guest Agent (the “qemu-ga” service) created
certain files with world-writable permissions when run in daemon mode
(the default mode). An unprivileged guest user could use this flaw to
consume all free space on the partition containing the qemu-ga log file, or
modify the contents of the log. When a UNIX domain socket transport was
explicitly configured to be used (not the default), an unprivileged guest
user could potentially use this flaw to escalate their privileges in the
guest. This update requires manual action. Refer below for details.
(CVE-2013-2007)

This update does not change the permissions of the existing log file or
the UNIX domain socket. For these to be changed, stop the qemu-ga service,
and then manually remove all “group” and “other” permissions on the
affected files, or remove the files.

Note that after installing this update, files created by the
guest-file-open QEMU Monitor Protocol (QMP) command will still continue to
be created with world-writable permissions for backwards compatibility.

This issue was discovered by Laszlo Ersek of Red Hat.

This update also fixes the following bugs:

• Previously, due to integer overflow in code calculations, the qemu-kvm
  utility was reporting incorrect memory size on QMP events when using the
  virtio balloon driver with more than 4 GB of memory. This update fixes the
  overflow in the code and qemu-kvm works as expected in the described
  scenario. (BZ#958750)

• When the set_link flag is set to “off” to change the status of a network
  card, the status is changed to “down” on the respective guest. Previously,
  with certain network cards, when such a guest was restarted, the status of
  the network card was unexpectedly reset to “up”, even though the network
  was unavailable. A patch has been provided to address this bug and the link
  status change is now preserved across restarts for all network cards.
  (BZ#927591)

All users of qemu-kvm should upgrade to these updated packages, which
contain backported patches to correct these issues. 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/2013-June/081937.html

Affected packages:
qemu-guest-agent
qemu-guest-agent-win32
qemu-img
qemu-kvm
qemu-kvm-tools

Upstream details at:
https://access.redhat.com/errata/RHSA-2013:0896