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Gentoo Linux Security Advisory                           GLSA 201703-07
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                                           https://security.gentoo.org/
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 Severity: Normal
    Title: Xen: Privilege Escalation
     Date: March 28, 2017
     Bugs: #609120
       ID: 201703-07

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Synopsis
=======
A vulnerability in Xen's bundled QEMU version might allow privilege
escalation.

Background
=========
Xen is a bare-metal hypervisor.

Affected packages
================
    -------------------------------------------------------------------
     Package              /     Vulnerable     /            Unaffected
    -------------------------------------------------------------------
  1  app-emulation/xen-tools     < 4.7.1-r8               >= 4.7.1-r8

Description
==========
In CIRRUS_BLTMODE_MEMSYSSRC mode the bitblit copy routine
cirrus_bitblt_cputovideo fails to check wethehr the specified memory
region is safe.

Impact
=====
A local attacker could potentially execute arbitrary code with
privileges of Xen (QEMU) process on the host, gain privileges on the
host system, or cause a Denial of Service condition.

Workaround
=========
Running guests in Paravirtualization (PV)  mode,  or running guests in
Hardware-assisted virtualizion (HVM) utilizing stub domains mitigate
the issue.

Running HVM guests with the device model in a stubdomain will mitigate
the issue.

Changing the video card emulation to stdvga (stdvga=1, vga="stdvga", in
the xl domain configuration) will avoid the vulnerability.

Resolution
=========
All Xen Tools users should upgrade to the latest version:

  # emerge --sync
  # emerge --ask --oneshot -v ">=app-emulation/xen-tools-4.7.1-r8"

References
=========
[ 1 ] CVE-2017-2620
      http://nvd.nist.gov/nvd.cfm?cvename=CVE-2017-2620

Availability
===========
This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

 https://security.gentoo.org/glsa/201703-07

Concerns?
========
Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users' machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
https://bugs.gentoo.org.

License
======
Copyright 2017 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

https://creativecommons.org/licenses/by-sa/2.5/