Red Hat Enterprise Linux 6: RHSA-2017:0309-01 Critical: qemu-kvm DoS Issue

Kernel-based Virtual Machine (KVM) is a full virtualization solution for Linux on a variety of architectures. The qemu-kvm packages provide the user-space component for running virtual machines that use KVM.
Security Fix(es):
* Quick emulator (Qemu) built with the Cirrus CLGD 54xx VGA emulator support is vulnerable to an out-of-bounds access issue. It could occur while copying VGA data via bitblt copy in backward mode. A privileged user inside a guest could use this flaw to crash the Qemu process resulting in DoS or potentially execute arbitrary code on the host with privileges of Qemu process on the host. (CVE-2017-2615)
* An out-of-bounds read-access flaw was found in the QEMU emulator built with IP checksum routines. The flaw could occur when computing a TCP/UDP packet's checksum, because a QEMU function used the packet's payload length without checking against the data buffer's size. A user inside a guest could use this flaw to crash the QEMU process (denial of service). (CVE-2016-2857)
Red Hat would like to thank Wjjzhang (Tencent.com Inc.) Li Qiang (360.cn Inc.) for reporting CVE-2017-2615 and Ling Liu (Qihoo 360 Inc.) for reporting CVE-2016-2857.
This update also fixes the following bug:
* Previously, rebooting a guest virtual machine more than 128 times in a short period of time caused the guest to shut down instead of rebooting, because the virtqueue was not cleaned properly. This update ensures that the virtqueue is cleaned more reliably, which prevents the described problem from occurring. (BZ#1408389)
All qemu-kvm users are advised to 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.