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Advisory

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             Xen Security Advisory CVE-2013-4371 / XSA-70
                               version 2

      use-after-free in libxl_list_cpupool under memory pressure

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

Public release.

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

If realloc(3) fails then libxl_list_cpupool will incorrectly return
the now-free original pointer.

IMPACT
======

An attacker may be able to cause a multithreaded toolstack using this
function to race against itself leading to heap corruption and a
potential DoS.

Depending on the malloc implementation code execution cannot be ruled
out.

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

The flaw is present in Xen 4.2 onwards.

Systems using the libxl toolstack library are vulnerable.

MITIGATION
==========

Not calling the libxl_list_cpupool function will avoid this issue.

Not allowing untrusted users access to toolstack functionality will
avoid this issue.

CREDITS
=======

This issue was discovered by Coverity Scan and Matthew Daley.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa70.patch             Xen 4.3.x, Xen 4.2.x, xen-unstable


$ sha256sum xsa70*.patch
2582d3d545903af475436145f7e459414ad9d9c61d5720992eeeec42de8dde56  xsa70.patch
$
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