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Bug 615274 (CVE-2017-7228) - app-emulation/xen: PV Guest Privilege Escalation (XSA-212)
Summary: app-emulation/xen: PV Guest Privilege Escalation (XSA-212)
Status: RESOLVED FIXED
Alias: CVE-2017-7228
Product: Gentoo Security
Classification: Unclassified
Component: Vulnerabilities (show other bugs)
Hardware: All Linux
: High major (vote)
Assignee: Gentoo Security
URL: https://xenbits.xen.org/xsa/advisory-...
Whiteboard: ~1 [noglsa/cve]
Keywords:
Depends on:
Blocks:
 
Reported: 2017-04-11 15:23 UTC by Yury German
Modified: 2017-05-03 21:20 UTC (History)
2 users (show)

See Also:
Package list:
Runtime testing required: ---


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Description Yury German Gentoo Infrastructure gentoo-dev 2017-04-11 15:23:06 UTC
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

            Xen Security Advisory CVE-2017-7228 / XSA-212
                              version 3

       x86: broken check in memory_exchange() permits PV guest breakout

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

Public release.

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.

CREDITS
=======

This issue was discovered by Jann Horn of Google Project Zero.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa212.patch           xen-unstable, Xen 4.8.x, Xen 4.7.x, Xen 4.6.x, Xen 4.5.x, Xen 4.4.x
Comment 1 Oleh 2017-05-03 06:24:39 UTC
according to https://www.xenproject.org/downloads/xen-archives/xen-project-48-series/xen-481.html
XSA-212 patch is applied in 4.8.1 release.
Comment 3 Yixun Lan gentoo-dev 2017-05-03 20:30:24 UTC
(In reply to Oleg from comment #1)

yes, this should be already fixed at 
 >=app-emulation/xen-4.7.2
 >=app-emulation/xen-4.8.1
thanks
Comment 4 Yury German Gentoo Infrastructure gentoo-dev 2017-05-03 21:20:31 UTC
Oleg thank you for bringing it to our attention.

Since our X86 version is not available (not keyword) this bug does not apply I am closing this bug and changing the whiteboard.