[kernel-xen] Xen Security Advisory 114 (CVE-2014-9065, CVE-2014-9066) - p2m lock starvation

[Steven Haigh]

     Xen Security Advisory CVE-2014-9065,CVE-2014-9066 / XSA-114
                              version 3

                       p2m lock starvation

UPDATES IN VERSION 3
====================

Public release.

ISSUE DESCRIPTION
=================

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
pressure.

IMPACT
======

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.

VULNERABLE SYSTEMS
==================

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.

MITIGATION
==========

There is no mitigation available for this issue.

CREDITS
=======

This issue was discovered by Andrew Cooper of Citrix.

RESOLUTION
==========

Tue Dec 09 2014 Steven Haigh <netwiz at crc.id.au> - 4.2.5-8
- XSA-114 (CVE-2014-9065) p2m lock starvation

Tue Dec 09 2014 Steven Haigh <netwiz at crc.id.au> - 4.4.1-8
- XSA-114 (CVE-2014-9065) p2m lock starvation

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