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Advisory

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            Xen Security Advisory CVE-2015-1563 / XSA-118
                              version 2

    arm: vgic: incorrect rate limiting of guest triggered logging

UPDATES IN VERSION 2
====================

CVE assigned.

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

On ARM systems the code which deals with virtualising the GIC
distributor would, under various circumstances, log messages on a
guest accessible code path without appropriate rate limiting.

IMPACT
======

A malicious guest could cause repeated logging to the hypervisor
console, leading to a Denial of Service attack.

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

Xen 4.4 and later systems running on ARM hardware are vulnerable.

x86 systems are not affected.

MITIGATION
==========

The problematic log messages are issued with priority Warning.

Therefore they can be rate limited by adding "loglvl=error/warning" to the
hypervisor command line or suppressed entirely by adding "loglvl=error".

NOTE REGARDING LACK OF EMBARGO
==============================

This bug was publicly reported on xen-devel, before it was appreciated
that there was a security problem.

CREDITS
=======

This issue was discovered by Julien Grall.

RESOLUTION
==========

Applying the appropriate attached patch(es) resolves this issue.

xsa118-unstable-4.5-{1,2}.patch       xen-unstable, Xen 4.5.x
xsa118-4.4.patch                      Xen 4.4.x

$ sha256sum xsa118*.patch
5741cfe408273bd80e1a03c21a5650f963d7103fd022c688730f55dcf5373433  xsa118-4.4.patch
ee24a4c5e12b67d7539f08b644080c87797f31b4402215cd4efbbc6114bffc25  xsa118-4.5-unstable-1.patch
bd532e3cd535fcdea51f43631a519012baff068cb62d2205fc25f2c823f031eb  xsa118-4.5-unstable-2.patch
$
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