RHSA-2010:0898 - Security Advisory

Topic

Updated kvm packages that fix one security issue are now available for Red
Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having moderate
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. KVM is a Linux kernel module built for
the standard Red Hat Enterprise Linux kernel.

A flaw was found in the way QEMU-KVM handled the reloading of fs and gs
segment registers when they had invalid selectors. A privileged host user
with access to "/dev/kvm" could use this flaw to crash the host (denial of
service). (CVE-2010-3698)

All KVM users should upgrade to these updated packages, which contain a
backported patch to correct this issue. Note: The procedure in the Solution
section must be performed before this update will 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
http://kbase.redhat.com/faq/docs/DOC-11259

The following procedure must be performed before this update will take
effect:

1) Stop all KVM guest virtual machines.

2) Either reboot the hypervisor machine or, as the root user, remove (using
"modprobe -r [module]") and reload (using "modprobe [module]") all of the
following modules which are currently running (determined using "lsmod"):
kvm, ksm, kvm-intel or kvm-amd.

3) Restart the KVM guest virtual machines.

Affected Products

• Red Hat Enterprise Linux Server 5 x86_64
• Red Hat Enterprise Linux Workstation 5 x86_64

Fixes

• BZ - 639879 - CVE-2010-3698 kvm: invalid selector in fs/gs causes kernel panic

CVEs

• CVE-2010-3698

References

• https://access.redhat.com/security/updates/classification/#moderate