RHSA-2012:1235 - 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
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. KVM is a Linux kernel module built
for the standard Red Hat Enterprise Linux kernel.

A flaw was found in the way QEMU handled VT100 terminal escape sequences
when emulating certain character devices. A guest user with privileges to
write to a character device that is emulated on the host using a virtual
console back-end could use this flaw to crash the qemu-kvm process on the
host or, possibly, escalate their privileges on the host. (CVE-2012-3515)

This flaw did not affect the default use of KVM. Affected configurations
were:

• When guests were started from the command line ("/usr/libexec/qemu-kvm"),

and without specifying a serial or parallel device that specifically does
not use a virtual console (vc) back-end. (Note that Red Hat does not
support invoking "qemu-kvm" from the command line on Red Hat Enterprise
Linux 5.)

• Guests that were managed via libvirt, such as when using Virtual Machine

Manager (virt-manager), but that have a serial or parallel device that uses
a virtual console back-end. By default, guests managed via libvirt will not
use a virtual console back-end for such devices.

Red Hat would like to thank the Xen project for reporting this issue.

All KVM users should upgrade to these updated packages, which 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
https://access.redhat.com/knowledge/articles/11258

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 - 851252 - CVE-2012-3515 qemu: VT100 emulation vulnerability

CVEs

• CVE-2012-3515

References

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