Bug 1434741 - (CVE-2017-7228, xsa212) CVE-2017-7228 xsa212 xen: x86: broken check in memory_exchange() permits PV guest breakout (XSA-212)
CVE-2017-7228 xsa212 xen: x86: broken check in memory_exchange() permits PV g...
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
high Severity high
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Assigned To: Red Hat Product Security
impact=important,public=20170404,repo...
: Security
Depends On: 1438804
Blocks:
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Reported: 2017-03-22 05:48 EDT by Adam Mariš
Modified: 2017-04-04 08:59 EDT (History)
12 users (show)

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Description Adam Mariš 2017-03-22 05:48:07 EDT
ISSUE DESCRIPTION
=================

The XSA-29 fix introduced an insufficient check on XENMEM_exchange
input, allowing the caller to drive hypervisor memory accesses outside
of the guest provided input/output arrays.

IMPACT
======

A malicious or buggy 64-bit PV guest may be able to access all of
system memory, allowing for all of privilege escalation, host crashes,
and information leaks.

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

All Xen versions are vulnerable.

Only x86 systems are affected.  ARM systems are not vulnerable.

The vulnerability is only exposed to 64-bit PV guests.  HVM guests and
32-bit PV guests can't exploit the vulnerability.

MITIGATION
==========

Running only HVM or 32-bit PV guests will avoid the vulnerability.

The vulnerability can be avoided if the guest kernel is controlled by
the host rather than guest administrator, provided that further steps
are taken to prevent the guest administrator from loading code into
the kernel (e.g. by disabling loadable modules etc) or from using
other mechanisms which allow them to run code at kernel privilege.

External References:

http://xenbits.xen.org/xsa/advisory-212.html

Acknowledgements:

Name: the Xen project
Comment 1 Adam Mariš 2017-04-04 08:59:45 EDT
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1438804]

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