Date: 11 December 2014
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AUSCERT External Security Bulletin Redistribution
Xen Security Advisory CVE-2014-9065,CVE-2014-9066 / XSA-114 version 3
11 December 2014
AusCERT Security Bulletin Summary
Operating System: UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Existing Account
CVE Names: CVE-2014-9066 CVE-2014-9065
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Xen Security Advisory CVE-2014-9065,CVE-2014-9066 / XSA-114
p2m lock starvation
UPDATES IN VERSION 3
The current read/write lock implementation is read-biased, which allows
a consistent stream of readers to starve writers indefinitely. There
are certain rwlocks where guests are capable of applying arbitrary read
A malicious guest administrator can deny service to other tasks. If
the NMI watchdog is active, a timeout might be triggered, resulting in
a host crash.
Xen 4.2 and later systems are vulnerable.
Xen 4.1 and earlier are not vulnerable in normal configurations. 4.1
and earlier are vulnerable only insofar as features are used which
have already been explicitly discounted for security support purposes
(TMEM, see XSA-15; XSM-based radical disaggregation, see XSA-77).
Only x86 systems offer avenues for attacking this vulnerability.
ARM systems do not and are therefore not vulnerable.
There is no mitigation available for this issue.
This issue was discovered by Andrew Cooper of Citrix.
Applying the appropriate attached patch resolves this issue in
practice for most systems. (CVE-2014-9065 refers to these fixed
In some deployments, large guests (more than around 30-40 VCPUs) may
still be able to trigger intermittent problems; a complete fix to this
issue requires substantial structural changes and is planned for Xen
4.6. (CVE-2014-9066 refers to these yet-to-be-fixed cases.)
xsa114-4.4.patch Xen 4.4.x
xsa114-4.3.patch Xen 4.3.x
xsa114-4.2.patch Xen 4.2.x
$ sha256sum xsa114*.patch
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