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	     Xen Security Advisory CVE-2012-5515 / XSA-31
                             version 3

  Several memory hypercall operations allow invalid extent order values

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

Public release.

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

Allowing arbitrary extent_order input values for XENMEM_decrease_reservation,
XENMEM_populate_physmap, and XENMEM_exchange can cause arbitrarily long time
being spent in loops without allowing vital other code to get a chance to
execute. This may also cause inconsistent state resulting at the completion
of these hypercalls.

IMPACT
======

A malicious guest administrator can cause Xen to hang.

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

All Xen versions are vulnerable.  However, older versions (not supporting
Populate-on-Demand, i.e. before 3.4) may only be theoretically affected.

MITIGATION
==========

Running only trusted guest kernels will avoid this vulnerability.

RESOLUTION
==========

Applying the appropriate attached patch resolves this issue.

xsa31-4.1.patch             Xen 4.1.x
xsa31-4.2-unstable.patch    Xen 4.2.x, xen-unstable


$ sha256sum xsa31*.patch
8e4bb43999d1a72d7f1b6ad3e66d0c173ca711c8145c5804b025eaa63d2c1691  xsa31-4.1.patch
090d0cca3eddaee798e5f06a8d5f469d47f874c657abcd6028248d949d36da81  xsa31-4.2-unstable.patch
$
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