Bug 1590979 – CVE-2018-12893 xen: x86 DB exception safety check can be triggered by a guest (XSA-265)

Bugzilla will be upgraded to version 5.0 on a still to be determined date in the near future. The original upgrade date has been delayed.

Bug 1590979 - (CVE-2018-12893) CVE-2018-12893 xen: x86 DB exception safety check can be triggered by a guest (XSA-265)

Summary:	CVE-2018-12893 xen: x86 DB exception safety check can be triggered by a guest...

Status:	CLOSED NOTABUG

Aliases:	CVE-2018-12893

Product:	Security Response
Classification:	Other
Component:	vulnerability (Show other bugs)
Sub Component:
Version:	unspecified
Hardware:	All Linux

Priority	medium Severity medium
Target Milestone:	---
Target Release:	---
Assigned To:	Red Hat Product Security
QA Contact:
Docs Contact:

URL:
Whiteboard:	impact=moderate,public=20180627:2100,...
Keywords:	Security

Depends On:	1595958
Blocks:	1590980
	Show dependency tree / graph

Reported:	2018-06-13 16:28 EDT by Laura Pardo
Modified:	2018-06-28 05:47 EDT (History)
CC List:	13 users (show)

See Also:
Fixed In Version:
Doc Type:	If docs needed, set a value
Doc Text:
Story Points:	---
Clone Of:
Environment:
Last Closed:	2018-06-28 05:31:19 EDT
Type:	---
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Add an attachment (proposed patch, testcase, etc.)

Groups: None (edit)

Description Laura Pardo 2018-06-13 16:28:33 EDT

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

One of the fixes in XSA-260 added some safety checks to help prevent Xen
livelocking with debug exceptions. Unfortunately, due to an oversight, at
least one of these safety checks can be triggered by a guest.

IMPACT
======

A malicious PV guest can crash Xen, leading to a Denial of Service.

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

All Xen systems which have applied the XSA-260 fix are vulnerable.

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

Only x86 PV guests can exploit the vulnerability. x86 HVM and PVH
guests cannot exploit the vulnerability.

An attacker needs to be able to control hardware debugging facilities to
exploit the vulnerability, but such permissions are typically available
to unprivileged users.

MITIGATION
==========

Running only x86 HVM or PVH guests will avoid the vulnerability.

Comment 1 Laura Pardo 2018-06-27 18:10:05 EDT

Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1595958]

Comment 2 Petr Matousek 2018-06-28 05:30:42 EDT

Acknowledgments:

Name: the Xen project
Upstream: Andrew Cooper (Citrix)

Note You need to log in before you can comment on or make changes to this bug.