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            Xen Security Advisory CVE-2018-15471 / XSA-270
                              version 3

           Linux netback driver OOB access in hash handling

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

CVE assigned.

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

Linux's netback driver allows frontends to control mapping of requests
to request queues.  When processing a request to set or change this
mapping, some input validation was missing or flawed.

IMPACT
======

A malicious or buggy frontend may cause the (usually privileged)
backend to make out of bounds memory accesses, potentially resulting
in one or more of privilege escalation, Denial of Service (DoS), or
information leaks.

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

Linux kernel versions from 4.7 onwards are affected.

MITIGATION
==========

There is no known mitigation.

CREDITS
=======

This issue was discovered by Felix Wilhelm of Google Project Zero.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa270.patch           Linux 4.7 ... 4.17

$ sha256sum xsa270*
392868c37c1fe0d16c36086208fd0fc045c1baf8ab9b207995bce72681cb8c54  xsa270.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is then no longer applicable.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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