Issued:
2010-03-01
Updated:
2010-03-01

RHSA-2010:0126 - Important: kvm security and bug fix update

Synopsis

Important: kvm security and bug fix update

Type/Severity

Security Advisory Important

Topic

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

This update has been rated as having important security impact by the Red Hat Security Response Team.

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 the x86 emulator loaded segment selectors (used for memory segmentation and protection) into segment registers. In some guest system configurations, an unprivileged guest user could leverage this flaw to crash the guest or possibly escalate their privileges within the guest. (CVE-2010-0419)

The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) while accessing debug registers. An unprivileged user in a guest could leverage this flaw to crash the guest. (CVE-2009-3722)

This update also fixes the following bugs:

With Red Hat Enterprise Virtualization, the virtio_blk_dma_restart_bh() function was previously used to handle write errors; however, a bug fix provided by the RHSA-2009:1659 update meant that read errors would also have to be handled by this function. The function was not updated for this, causing read errors to be resubmitted as writes. This caused guest image corruption in some cases.

Additionally, the return values of the bdrv_aio_write() and bdrv_aio_read() functions were ignored. If an immediate failure occurred in one of these functions, errors would be missed and the guest could hang or read corrupted data. (BZ#562776)

All KVM users should upgrade to these updated packages, which contain backported patches to resolve 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 that all previously-released errata relevant to your system have been applied.

This update is available via Red Hat Network. Details on how to use the Red Hat Network to apply this update are available at This content is not included.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

ProductVersionArch
Red Hat Enterprise Linux for x86_64 - Extended Update Support5.4x86_64
Red Hat Enterprise Linux Workstation5x86_64
Red Hat Enterprise Linux Server5x86_64

Updated Packages

  • kvm-83-105.el5_4.27.src.rpm
  • kmod-kvm-83-105.el5_4.27.x86_64.rpm
  • kvm-tools-83-105.el5_4.27.x86_64.rpm
  • kvm-83-105.el5_4.27.x86_64.rpm
  • kvm-qemu-img-83-105.el5_4.27.x86_64.rpm

Fixes

CVEs

References

Additional information