RHSA-2012:0050 - Security Advisory

Topic

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.

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.

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

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.2 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Storage 2.0 x86_64
• Red Hat Gluster Storage Server for On-premise 2.0 x86_64
• Red Hat Storage for Public Cloud (via RHUI) 2.0 x86_64
• Red Hat Enterprise Linux Server - AUS 6.2 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.2 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64

Fixes

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

CVEs

• CVE-2012-0029

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/kb/docs/DOC-67874
• https://rhn.redhat.com/errata/RHSA-2011-1849.html
• https://rhn.redhat.com/errata/RHBA-2012-0013.html