Red Hat: RHSA-2014:0927-01 Moderate qemu-kvm Security Update

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.
Two integer overflow flaws were found in the QEMU block driver for QCOW version 1 disk images. A user able to alter the QEMU disk image files loaded by a guest could use either of these flaws to corrupt QEMU process memory on the host, which could potentially result in arbitrary code execution on the host with the privileges of the QEMU process. (CVE-2014-0222, CVE-2014-0223)
Multiple buffer overflow, input validation, and out-of-bounds write flaws were found in the way virtio, virtio-net, virtio-scsi, usb, and hpet drivers of QEMU handled state loading after migration. A user able to alter the savevm data (either on the disk or over the wire during migration) could use either of these flaws to corrupt QEMU process memory on the (destination) host, which could potentially result in arbitrary code execution on the host with the privileges of the QEMU process. (CVE-2013-4148, CVE-2013-4149, CVE-2013-4150, CVE-2013-4151, CVE-2013-4527, CVE-2013-4529, CVE-2013-4535, CVE-2013-4536, CVE-2013-4541, CVE-2013-4542, CVE-2013-6399, CVE-2014-0182, CVE-2014-3461)
These issues were discovered by Michael S. Tsirkin, Anthony Liguori and Michael Roth of Red Hat: CVE-2013-4148, CVE-2013-4149, CVE-2013-4150, CVE-2013-4151, CVE-2013-4527, CVE-2013-4529, CVE-2013-4535, CVE-2013-4536, CVE-2013-4541, CVE-2013-4542, CVE-2013-6399, CVE-2014-0182, and CVE-2014-3461.
This update also fixes the following bugs:
* Previously, QEMU did not free pre-allocated zero clusters correctly and the clusters under some circumstances leaked. With this update, pre-allocated zero clusters are freed appropriately and the cluster leaks no longer occur. (BZ#1110188)
* Prior to this update, the QEMU command interface did not properly handle resizing of cache memory during guest migration, causing QEMU to terminate unexpectedly with a segmentation fault and QEMU to fail. This update fixes the related code and QEMU no longer crashes in the described situation. (BZ#1110191)
* Previously, when a guest device was hot unplugged, QEMU correctly removed the corresponding file descriptor watch but did not re-create it after the device was re-connected. As a consequence, the guest became unable to receive any data from the host over this device. With this update, the file descriptor's watch is re-created and the guest in the above scenario can communicate with the host as expected. (BZ#1110219)
* Previously, the QEMU migration code did not account for the gaps caused by hot unplugged devices and thus expected more memory to be transferred during migrations. As a consequence, guest migration failed to complete after multiple devices were hot unplugged. In addition, the migration info text displayed erroneous values for the "remaining ram" item. With this update, QEMU calculates memory after a device has been unplugged correctly, and any subsequent guest migrations proceed as expected. (BZ#1110189)
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.