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Advisory

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             Xen Security Advisory CVE-2013-4369 / XSA-68
                               version 2

     possible null dereference when parsing vif ratelimiting info

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

Public release.

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

The libxlu library function xlu_vif_parse_rate does not properly
handle inputs which consist solely of the '@' character, leading to a
NULL pointer dereference.

IMPACT
======

A toolstack which allows untrusted users to specify an arbitrary
configuration for the VIF rate can be subjected to a DOS.

The only known user of this library is the xl toolstack which does not
have a central long running daemon and therefore the impact is limited
to crashing the process which is creating the domain, which exists
only to service a single domain.

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

The vulnerable code is present from Xen 4.2 onwards.

MITIGATION
==========

Disallowing untrusted users from specifying arbitrary VIF rate limits
will avoid this issue.

CREDITS
=======

This issue was discovered by Coverity Scan and Matthew Daley.

RESOLUTION
==========

Applying the attached patch resolves this issue in all branches

xsa68.patch        xen-unstable, Xen 4.3.x, Xen 4.2.x

$ sha256sum xsa68*.patch
64716cb49696298e0bbd9556fe9d6f559a4e2785081e28d50607317b6e27ba32  xsa68.patch
$
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