RHSA-2015:0869 - Security Advisory

Topic

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

Red Hat Product Security has rated this update as having Important security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links 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.

It was found that KVM's Write to Model Specific Register (WRMSR)
instruction emulation would write non-canonical values passed in by the
guest to certain MSRs in the host's context. A privileged guest user could
use this flaw to crash the host. (CVE-2014-3610)

A race condition flaw was found in the way the Linux kernel's KVM subsystem
handled PIT (Programmable Interval Timer) emulation. A guest user who has
access to the PIT I/O ports could use this flaw to crash the host.
(CVE-2014-3611)

Red Hat would like to thank Lars Bull of Google and Nadav Amit for
reporting the CVE-2014-3610 issue, and Lars Bull of Google for reporting
the CVE-2014-3611 issue.

All kvm users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. 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.

For details on how to apply this update, refer to:

https://access.redhat.com/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 - 1144878 - CVE-2014-3611 kernel: kvm: PIT timer race condition
• BZ - 1144883 - CVE-2014-3610 kernel: kvm: noncanonical MSR writes

CVEs

• CVE-2014-3611
• CVE-2014-3610

References

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