(Red Hat Issues Fix for KVM) Linux Kernel KVM PIT Timer Race Condition Lets Local Guest Users Deny Service on the Host System
SecurityTracker Alert ID: 1032184|
SecurityTracker URL: http://securitytracker.com/id/1032184
(Links to External Site)
Date: Apr 22 2015
Denial of service via local system|
Fix Available: Yes Vendor Confirmed: Yes |
A vulnerability was reported in the Linux Kernel. A local user on a KVM guest system can cause denial of service conditions on the host system. KVM is affected.|
A local user on a guest operating system can trigger a race condition in PIT emulation in the KVM subsystem to cause the target host operating system to crash.
The vulnerability resides in the __kvm_migrate_pit_timer() function in 'arch/x86/kvm/i8254.c'.
A local user on a guest system can cause the target host system to crash.|
Red Hat has issued an advisory for KVM.|
The Red Hat advisory is available at:
Vendor URL: www.kernel.org/ (Links to External Site)
|Underlying OS: Linux (Red Hat Enterprise)|
|Underlying OS Comments: 5|
This archive entry is a follow-up to the message listed below.|
Source Message Contents
Subject: [RHSA-2015:0869-01] Important: kvm security update|
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Red Hat Security Advisory
Synopsis: Important: kvm security update
Advisory ID: RHSA-2015:0869-01
Product: Red Hat Enterprise Linux
Advisory URL: https://rhn.redhat.com/errata/RHSA-2015-0869.html
Issue date: 2015-04-22
CVE Names: CVE-2014-3610 CVE-2014-3611
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.
2. Relevant releases/architectures:
RHEL Desktop Multi OS (v. 5 client) - x86_64
RHEL Virtualization (v. 5 server) - x86_64
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.
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.
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:
The following procedure must be performed before this update will take
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.
5. Bugs fixed (https://bugzilla.redhat.com/):
1144878 - CVE-2014-3611 kernel: kvm: PIT timer race condition
1144883 - CVE-2014-3610 kernel: kvm: noncanonical MSR writes
6. Package List:
RHEL Desktop Multi OS (v. 5 client):
RHEL Virtualization (v. 5 server):
These packages are GPG signed by Red Hat for security. Our key and
details on how to verify the signature are available from
The Red Hat security contact is <firstname.lastname@example.org>. More contact
details at https://access.redhat.com/security/team/contact/
Copyright 2015 Red Hat, Inc.
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