RHSA-2011:0919 - Security Advisory

Topic

Updated qemu-kvm packages that fix two security issues and one bug are now
available for Red Hat Enterprise Linux 6.

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. qemu-kvm is the user-space component
for running virtual machines using KVM.

It was found that the virtio subsystem in qemu-kvm did not properly
validate virtqueue in and out requests from the guest. A privileged guest
user could use this flaw to trigger a buffer overflow, allowing them to
crash the guest (denial of service) or, possibly, escalate their privileges
on the host. (CVE-2011-2212)

It was found that the virtio_queue_notify() function in qemu-kvm did not
perform sufficient input validation on the value later used as an index
into the array of virtqueues. An unprivileged guest user could use this
flaw to crash the guest (denial of service) or, possibly, escalate their
privileges on the host. (CVE-2011-2512)

Red Hat would like to thank Nelson Elhage for reporting CVE-2011-2212.

This update also fixes the following bug:

• A bug was found in the way vhost (in qemu-kvm) set up mappings with the

host kernel's vhost module. This could result in the host kernel's vhost
module not having a complete view of a guest system's memory, if that guest
had more than 4 GB of memory. Consequently, hot plugging a vhost-net
network device and restarting the guest may have resulted in that device no
longer working. (BZ#701771)

All users of qemu-kvm should upgrade to these updated packages, which
contain backported patches to resolve these issues. 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 6.1 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 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 Enterprise Linux Server - Extended Update Support from RHUI 6.1 x86_64
• Red Hat Virtual Storage Appliance (from RHUI) 6.1 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64

Fixes

• BZ - 713589 - CVE-2011-2212 qemu-kvm: virtqueue: too-large indirect descriptor buffer overflow
• BZ - 717399 - CVE-2011-2512 qemu-kvm: OOB memory access caused by negative vq notifies

CVEs

• CVE-2011-2512
• CVE-2011-2212

References

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