Xen.org security team
2013-Jun-26 13:19 UTC
Xen Security Advisory 58 (CVE-2013-1432) - Page reference counting error due to XSA-45/CVE-2013-1918 fixes
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Xen Security Advisory CVE-2013-1432 / XSA-58
version 2
Page reference counting error due to XSA-45/CVE-2013-1918 fixes
UPDATES IN VERSION 2
===================
Public release. Credits section added.
ISSUE DESCRIPTION
================
The XSA-45/CVE-2013-1918 patch making error handling paths preemptible broke
page reference counting by not retaining a reference on pages stored for
deferred cleanup. This would lead to the hypervisor prematurely attempting to
free the page, generally crashing upon finding the page still in use.
CREDITS
======
Thanks to Andrew Cooper and the Citrix XenServer team for discovering
and reporting this vulnerability, and helping investigate it.
IMPACT
=====
Malicious or buggy PV guest kernels can mount a denial of service attack
affecting the whole system. It can''t be excluded that this could also
be
exploited to mount a privilege escalation attack.
VULNERABLE SYSTEMS
=================
All Xen versions having the XSA-45/CVE-2013-1918 fixes applied are vulnerable.
The vulnerability is only exposed by PV guests.
MITIGATION
=========
Running only HVM guests, or PV guests with trusted kernels, will avoid this
vulnerability.
RESOLUTION
=========
Applying the appropriate attached patch resolves this issue.
xsa58-4.1.patch Xen 4.1.x
xsa58-4.2.patch Xen 4.2.x
xsa58-unstable.patch xen-unstable
$ sha256sum xsa58*.patch
3623ec87e5a2830f0d41de19a8e448d618954973c3264727a1f3a095f15a8641
xsa58-4.1.patch
194d6610fc38b767d643e5d58a1268f45921fb35e309b47aca6a388b861311c2
xsa58-4.2.patch
2c94b099d7144d03c0f7f44e892a521537fc040d11bc46f84a2438eece46a0f5
xsa58-unstable.patch
$
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