RHSA-2013:0727 - Security Advisory

Topic

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

The Red Hat Security Response Team 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.

A flaw was found in the way KVM handled guest time updates when the buffer
the guest registered by writing to the MSR_KVM_SYSTEM_TIME machine state
register (MSR) crossed a page boundary. A privileged guest user could use
this flaw to crash the host or, potentially, escalate their privileges,
allowing them to execute arbitrary code at the host kernel level.
(CVE-2013-1796)

A potential use-after-free flaw was found in the way KVM handled guest time
updates when the GPA (guest physical address) the guest registered by
writing to the MSR_KVM_SYSTEM_TIME machine state register (MSR) fell into a
movable or removable memory region of the hosting user-space process (by
default, QEMU-KVM) on the host. If that memory region is deregistered from
KVM using KVM_SET_USER_MEMORY_REGION and the allocated virtual memory
reused, a privileged guest user could potentially use this flaw to
escalate their privileges on the host. (CVE-2013-1797)

A flaw was found in the way KVM emulated IOAPIC (I/O Advanced Programmable
Interrupt Controller). A missing validation check in the
ioapic_read_indirect() function could allow a privileged guest user to
crash the host, or read a substantial portion of host kernel memory.
(CVE-2013-1798)

Red Hat would like to thank Andrew Honig of Google for reporting all of
these issues.

All users of kvm are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. Note that 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 for x86_64 - Extended Update Support 5.9 x86_64
• Red Hat Enterprise Linux Server - AUS 5.9 x86_64
• Red Hat Enterprise Linux Workstation 5 x86_64

Fixes

• BZ - 917012 - CVE-2013-1796 kernel: kvm: buffer overflow in handling of MSR_KVM_SYSTEM_TIME
• BZ - 917013 - CVE-2013-1797 kernel: kvm: after free issue with the handling of MSR_KVM_SYSTEM_TIME
• BZ - 917017 - CVE-2013-1798 kernel: kvm: out-of-bounds access in ioapic indirect register reads

CVEs

• CVE-2013-1798
• CVE-2013-1796
• CVE-2013-1797

References

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