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Red Hat 5: RHSA-2010-0998-01 Low: KVM Security Flaw Resolved

red hat
Calendar Grey December 20, 2010
Dist Redhat Esm H88
Enhanced kernel virtual machine packages resolve vulnerabilities and glitches for Red Hat Enterprise Linux 5, exhibiting minimal risk.
Updated kvm packages that fix one security issue and three bugs are now available for Red Hat Enterprise Linux 5

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

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.

Summary

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 some structure padding and reserved fields in certain data structures in QEMU-KVM were not initialized properly before being copied to user-space. A privileged host user with access to "/dev/kvm" could use this flaw to leak kernel stack memory to user-space. (CVE-2010-3881)
Red Hat would like to thank Vasiliy Kulikov for reporting this issue.
This update also fixes the following bugs:
* The 'kvm_amd' kernel module did not initialize the TSC (Time Stamp Counter) offset in the VMCB (Virtual Machine Control Block) correctly. After a vCPU (virtual CPU) has been created, the TSC offset in the VMCB should have a negative value so that the virtual machine will see TSC values starting at zero. However, the TSC offset was set to zero and therefore the virtual machine saw the same TSC value as the host. With this update, the TSC offset has been updated to show the correct values. (BZ#656984)
* Setting the boot settings of a virtual machine to, firstly, boot from PXE and, secondly, to boot from the hard drive would result in a PXE boot loop, that is, the virtual machine would not continue to boot from the hard drive if the PXE boot failed. This was caused by a flaw in the 'bochs-bios' (part of KVM) code. With this update, after a virtual machine tries to boot from PXE and fails, it continues to boot from a hard drive if there is one present. (BZ#659850)
* If a 64-bit Red Hat Enterprise Linux 5.5 virtual machine was migrated to another host with a different CPU clock speed, the clock of that virtual machine would consistently lose or gain time (approximately half a second for every second the host is running). On machines that do not use the kvm clock, the network time protocol daemon (ntpd) could correct the time drifts caused by migration. However, using the pvclock caused the time to change consistently. This was due to flaws in the save/load functions of pvclock. With this update, the issue has been fixed and migrating a virtual machine no longer causes time drift. (BZ#660239)
All KVM users should 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.

Topics%20covered

Topics Covered

security advisory security update Red Hat bug fix low severity virtualization KVM

References

https://access.redhat.com/security/cve/CVE-2010-3881 https://access.redhat.com/security/updates/classification/#low

Package List

RHEL Desktop Multi OS (v. 5 client):
Source:
x86_64: kmod-kvm-83-164.el5_5.30.x86_64.rpm kvm-83-164.el5_5.30.x86_64.rpm kvm-debuginfo-83-164.el5_5.30.x86_64.rpm kvm-qemu-img-83-164.el5_5.30.x86_64.rpm kvm-tools-83-164.el5_5.30.x86_64.rpm
RHEL Virtualization (v. 5 server):
Source:
x86_64: kmod-kvm-83-164.el5_5.30.x86_64.rpm kvm-83-164.el5_5.30.x86_64.rpm kvm-debuginfo-83-164.el5_5.30.x86_64.rpm kvm-qemu-img-83-164.el5_5.30.x86_64.rpm kvm-tools-83-164.el5_5.30.x86_64.rpm
These packages are GPG signed by Red Hat for security. Our key and details on how to verify the signature are available from https://access.redhat.com/security/team/key/#package


Severity
low
Lowest
Low
Medium
High
Critical

Advisory ID: RHSA-2010:0998-01
Product: Red Hat Enterprise Linux
Advisory URL: https://access.redhat.com/errata/RHSA-2010:0998.html
Issue date: 2010-12-20

Topic

Updated kvm packages that fix one security issue and three bugs are nowavailable for Red Hat Enterprise Linux 5.The Red Hat Security Response Team has rated this update as having lowsecurity impact. A Common Vulnerability Scoring System (CVSS) base score,which gives a detailed severity rating, is available from the CVE link inthe References section.

Topics%20covered

Topics Covered

security advisory security update Red Hat bug fix low severity virtualization KVM

Relevant Releases Architectures

RHEL Desktop Multi OS (v. 5 client) - x86_64

RHEL Virtualization (v. 5 server) - x86_64

Bugs Fixed

649920 - CVE-2010-3881 kvm: arch/x86/kvm/x86.c: reading uninitialized stack memory

656984 - TSC offset of virtual machines is not initialized correctly by 'kvm_amd' kernel module.

659850 - If VM boot seq. is set up as nc (PXE then disk) the VM is always stuck on trying to PXE boot

660239 - clock drift when migrating a guest between mis-matched CPU clock speed

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