7.4 - RHSA-2012:0050

Problem Description:

Updated qemu-kvm packages that fix one security issue, one bug, and add one enhancement are now available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having important security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Desktop (v. 6) - x86_64 Red Hat Enterprise Linux HPC Node (v. 6) - x86_64 Red Hat Enterprise Linux Server (v. 6) - x86_64 Red Hat Enterprise Linux Workstation (v. 6) - x86_64

3. Description:

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.

A heap overflow flaw was found in the way QEMU-KVM emulated the e1000 network interface card. A privileged guest user in a virtual machine whose network interface is configured to use the e1000 emulated driver could use this flaw to crash the host or, possibly, escalate their privileges on the host. (CVE-2012-0029)

Red Hat would like to thank Nicolae Mogoreanu for reporting this issue.

This update also fixes the following bug:

* qemu-kvm has a "scsi" option, to be used, for example, with the "-device" option: "-device virtio-blk-pci,drive=[drive name],scsi=off". Previously, however, it only masked the feature bit, and did not reject SCSI commands if a malicious guest ignored the feature bit and issued a request. This update corrects this issue. The "scsi=off" option can be used to mitigate the virtualization aspect of CVE-2011-4127 before the RHSA-2011:1849 kernel update is installed on the host.

This mitigation is only required if you do not have the RHSA-2011:1849 kernel update installed on the host and you are using raw format virtio disks backed by a partition or LVM volume.

If you run guests by invoking /usr/libexec/qemu-kvm directly, use the "-global virtio-blk-pci.scsi=off" option to apply the mitigation. If you are using libvirt, as recommended by Red Hat, and have the RHBA-2012:0013 libvirt update installed, no manual action is required: guests will automatically use "scsi=off". (BZ#767721)

Note: After installing the RHSA-2011:1849 kernel update, SCSI requests issued by guests via the SG_IO IOCTL will not be passed to the underlying block device when using raw format virtio disks backed by a partition or LVM volume, even if "scsi=on" is used.

As well, this update adds the following enhancement:

* Prior to this update, qemu-kvm was not built with RELRO or PIE support. qemu-kvm is now built with full RELRO and PIE support as a security enhancement. (BZ#767906)

All users of qemu-kvm should upgrade to these updated packages, which correct these issues and add this enhancement. 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.

4. Solution:

Before applying this update, make sure all previously-released errata relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the Red Hat Network to apply this update are available at https://access.redhat.com/kb/docs/DOC-11259

5. Bugs fixed (http://bugzilla.redhat.com/):

772075 - CVE-2012-0029 qemu-kvm: e1000: process_tx_desc legacy mode packets heap overflow