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Advisory

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            Xen Security Advisory CVE-2017-14316 / XSA-231
                               version 3

               Missing NUMA node parameter verification

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

Updated metadata file

Public release.

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

The function `alloc_heap_pages` allows callers to specify the first
NUMA node that should be used for allocations through the `memflags`
parameter; the node is extracted using the `MEMF_get_node` macro.

While the function checks to see if the special constant
`NUMA_NO_NODE` is specified, it otherwise does not handle the case
where `node >= MAX_NUMNODES`.  This allows an out-of-bounds access
to an internal array.

IMPACT
======

An attacker using crafted hypercalls can execute arbitrary code within
Xen.

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

All versions of Xen are affected.

Both ARM and x86 are affected.

Both systems running HVM guests and system running PV guests are
affected.

MITIGATION
==========

No known mitigation.

CREDITS
=======

This issue was discovered by Matthew Daley.

RESOLUTION
==========

Applying the appropriate attached patch resolves this issue.

xsa231.patch           xen-unstable
xsa231-4.9.patch       Xen 4.9, Xen 4.8
xsa231-4.7.patch       Xen 4.7, Xen 4.6
xsa231-4.5.patch       Xen 4.5

$ sha256sum xsa231*
4255d2bc4ca668e7abcbf8256b0a8f21acef2a47a06d626aad6d22c685034587  xsa231.meta
b72af3fb8c44925ea7973533e8a8701becfc194f3e1c97f12af0392e1edd16a3  xsa231.patch
d9853b2d2649679d8810bd7e93f7b51bd9fefb3472da60ae464bde88aae3389c  xsa231-4.5.patch
ce29b56a0480f4835b37835b351e704d204bb0ccd22325f487127aa2776cc2cf  xsa231-4.7.patch
71a53a5133c8d4e381dd0e3e54205d31dea545ab62b261084dd3aea140f88cad  xsa231-4.9.patch
$

DEPLOYMENT DURING EMBARGO
=========================

Deployment of the patches and/or mitigations described above (or
others which are substantially similar) is permitted during the
embargo, even on public-facing systems with untrusted guest users and
administrators.

But: Distribution of updated software is prohibited (except to other
members of the predisclosure list).

Predisclosure list members who wish to deploy significantly different
patches and/or mitigations, please contact the Xen Project Security
Team.


(Note: this during-embargo deployment notice is retained in
post-embargo publicly released Xen Project advisories, even though it
is then no longer applicable.  This is to enable the community to have
oversight of the Xen Project Security Team's decisionmaking.)

For more information about permissible uses of embargoed information,
consult the Xen Project community's agreed Security Policy:
  http://www.xenproject.org/security-policy.html
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