Bug 995789 (CVE-2016-7093) - VUL-0: CVE-2016-7093: xen: x86: Mishandling of instruction pointer truncation during emulation (XSA-186)
Summary: VUL-0: CVE-2016-7093: xen: x86: Mishandling of instruction pointer truncation...
Status: RESOLVED FIXED
Alias: CVE-2016-7093
Product: SUSE Security Incidents
Classification: Novell Products
Component: Incidents (show other bugs)
Version: unspecified
Hardware: Other Other
: P3 - Medium : Major
Target Milestone: ---
Assignee: Security Team bot
QA Contact: Security Team bot
URL:
Whiteboard: CVSSv2:RedHat:CVE-2016-7093:6.0:(AV:N...
Keywords:
Depends on:
Blocks:
 
Reported: 2016-08-26 13:52 UTC by Johannes Segitz
Modified: 2016-10-13 19:19 UTC (History)
3 users (show)

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Found By: ---
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Blocker: ---
Marketing QA Status: ---
IT Deployment: ---

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Comment 3 Swamp Workflow Management 2016-08-26 22:00:50 UTC 
bugbot adjusting priority
Comment 9 Johannes Segitz 2016-09-08 14:24:17 UTC 
            Xen Security Advisory CVE-2016-7093 / XSA-186
                              version 4

      x86: Mishandling of instruction pointer truncation during emulation

UPDATES IN VERSION 4
====================

Public release.

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

When emulating HVM instructions, Xen uses a small i-cache for fetches
from guest memory.  The code that handles cache misses does not check
if the address from which it fetched lies within the cache before
blindly writing to it.  As such it is possible for the guest to
overwrite hypervisor memory.

It is currently believed that the only way to trigger this bug is to
use the way that Xen currently incorrectly wraps CS:IP in 16 bit
modes.  The included patch prevents such wrapping.

IMPACT
======

A malicious HVM guest administrator can escalate their privilege to that
of the host.

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

Xen versions 4.7.0 and later are vulnerable.
Xen releases 4.6.3 and 4.5.3 are vulnerable.

Xen releases 4.6.0 to 4.6.2 inclusive are NOT vulnerable.
Xen releases 4.5.2 and earlier are NOT vulnerable.

The vulnerability is only exposed to HVM guests on x86 hardware.

The vulnerability is not exposed to x86 PV guests, or ARM guests.

MITIGATION
==========
Running only PV guests will avoid this vulnerability.

CREDITS
=======

This issue was discovered by Brian Marcotte.

RESOLUTION
==========

Applying the first patch will resolve the issue.

Users wishing to independently verify the correctness of the fix may
find the second patch helpful.  The second patch makes it easier to
use the "fep" (Force Emulation Prefix) feature to reproduce the
erroneous condition in a test environment.  The "fep" feature requires
explicit enablement on the hypervisor command line, and is unsuitable
for production systems.  Accordingly, applying the second patch does
not affect production systems and does not improve security.

Xen version     First patch               Second patch
 xen-unstable:   xsa186-0001-*.patch       xsa186-0002-*.patch
 Xen 4.7.x:      xsa186-0001-*.patch       xsa186-4.7-0002-*.patch
 Xen 4.6.3:      xsa186-0001-*.patch       xsa186-4.6-0002-*.patch
 Xen 4.5.3:      xsa186-0001-*.patch       xsa186-4.6-0002-*.patch

$ sha256sum xsa186*
f2082a36d968a47e477bb5082d0e0aaa58e6cb3dc20b26389f043a9b7b595fa6  xsa186-0001-x86-emulate-Correct-boundary-interactions-of-emulate.patch
412fa58edcbd1c7fdbfec7e28898cf98585593e6a24ccfb088dc0b84715286a5  xsa186-0002-hvm-fep-Allow-testing-of-instructions-crossing-the-1.patch
7482a823c3443e26dee1111c4904162845eaa9f826aa7bf8348007406d91bddd  xsa186-4.6-0002-hvm-fep-Allow-testing-of-instructions-crossing-the.patch
5a826a32763d82ac83c924f8c89d12aae5f069a4cbc7d5193aa8413a02b6dc05  xsa186-4.7-0002-hvm-fep-Allow-testing-of-instructions-crossing-the.patch
Comment 10 Charles Arnold 2016-10-03 17:22:40 UTC 
Submitted for,

SLE-11-SP4
SLE-12
SLE-12-SP1
Comment 11 Swamp Workflow Management 2016-10-07 12:12:08 UTC 
SUSE-SU-2016:2473-1: An update that solves 10 vulnerabilities and has 11 fixes is now available.

Category: security (important)
Bug References: 953518,955104,959330,959552,970135,971949,988675,988676,990500,990970,991934,992224,993665,994421,994625,994761,994772,994775,995785,995789,995792
CVE References: CVE-2016-6258,CVE-2016-6259,CVE-2016-6833,CVE-2016-6834,CVE-2016-6835,CVE-2016-6836,CVE-2016-6888,CVE-2016-7092,CVE-2016-7093,CVE-2016-7094
Sources used:
SUSE Linux Enterprise Software Development Kit 12-SP1 (src):    xen-4.5.3_10-20.1
SUSE Linux Enterprise Server 12-SP1 (src):    xen-4.5.3_10-20.1
SUSE Linux Enterprise Desktop 12-SP1 (src):    xen-4.5.3_10-20.1
Comment 12 Swamp Workflow Management 2016-10-11 17:19:31 UTC 
openSUSE-SU-2016:2494-1: An update that solves 46 vulnerabilities and has 17 fixes is now available.

Category: security (important)
Bug References: 900418,949889,953339,953362,953518,954872,955104,958848,959330,959552,961100,961600,963161,964427,970135,971949,973188,973631,974038,975130,975138,975907,976058,976111,978164,978295,978413,979620,979670,980716,980724,981264,981276,982024,982025,982026,982224,982225,982286,982695,982960,983973,983984,984981,985503,986586,988675,988676,990500,990843,990923,990970,991934,992224,993665,994421,994625,994761,994772,994775,995785,995789,995792
CVE References: CVE-2014-3615,CVE-2014-3672,CVE-2015-7512,CVE-2015-8504,CVE-2015-8558,CVE-2015-8568,CVE-2015-8613,CVE-2015-8743,CVE-2016-1714,CVE-2016-1981,CVE-2016-3158,CVE-2016-3159,CVE-2016-3710,CVE-2016-3712,CVE-2016-3960,CVE-2016-4001,CVE-2016-4002,CVE-2016-4020,CVE-2016-4037,CVE-2016-4439,CVE-2016-4441,CVE-2016-4453,CVE-2016-4454,CVE-2016-4480,CVE-2016-4952,CVE-2016-4962,CVE-2016-4963,CVE-2016-5105,CVE-2016-5106,CVE-2016-5107,CVE-2016-5126,CVE-2016-5238,CVE-2016-5337,CVE-2016-5338,CVE-2016-5403,CVE-2016-6258,CVE-2016-6259,CVE-2016-6351,CVE-2016-6833,CVE-2016-6834,CVE-2016-6835,CVE-2016-6836,CVE-2016-6888,CVE-2016-7092,CVE-2016-7093,CVE-2016-7094
Sources used:
openSUSE Leap 42.1 (src):    xen-4.5.3_10-15.2
Comment 13 Swamp Workflow Management 2016-10-11 17:30:13 UTC 
openSUSE-SU-2016:2497-1: An update that solves 38 vulnerabilities and has 20 fixes is now available.

Category: security (important)
Bug References: 953339,953362,953518,954872,955399,958848,961100,961600,963161,964427,970135,971949,973188,973631,974038,975130,975138,975907,976058,976111,978164,978295,978413,979035,979620,979670,980716,980724,981264,981276,982024,982025,982026,982224,982225,982286,982695,982960,983973,983984,984981,985503,986586,988675,990843,990923,990970,991934,992224,994421,994625,994761,994772,994775,995785,995789,995792,997731
CVE References: CVE-2014-3615,CVE-2014-3672,CVE-2016-3158,CVE-2016-3159,CVE-2016-3710,CVE-2016-3712,CVE-2016-3960,CVE-2016-4001,CVE-2016-4002,CVE-2016-4020,CVE-2016-4037,CVE-2016-4439,CVE-2016-4441,CVE-2016-4453,CVE-2016-4454,CVE-2016-4480,CVE-2016-4952,CVE-2016-4962,CVE-2016-4963,CVE-2016-5105,CVE-2016-5106,CVE-2016-5107,CVE-2016-5126,CVE-2016-5238,CVE-2016-5337,CVE-2016-5338,CVE-2016-5403,CVE-2016-6258,CVE-2016-6351,CVE-2016-6833,CVE-2016-6834,CVE-2016-6835,CVE-2016-6836,CVE-2016-6888,CVE-2016-7092,CVE-2016-7093,CVE-2016-7094,CVE-2016-7154
Sources used:
openSUSE 13.2 (src):    xen-4.4.4_05-49.1
Comment 14 Swamp Workflow Management 2016-10-12 13:14:08 UTC 
SUSE-SU-2016:2507-1: An update that solves 10 vulnerabilities and has 8 fixes is now available.

Category: security (important)
Bug References: 966467,970135,971949,988675,990970,991934,992224,993507,994136,994421,994625,994761,994772,994775,995785,995789,995792,997731
CVE References: CVE-2016-6258,CVE-2016-6833,CVE-2016-6834,CVE-2016-6835,CVE-2016-6836,CVE-2016-6888,CVE-2016-7092,CVE-2016-7093,CVE-2016-7094,CVE-2016-7154
Sources used:
SUSE Linux Enterprise Software Development Kit 11-SP4 (src):    xen-4.4.4_08-40.2
SUSE Linux Enterprise Server 11-SP4 (src):    xen-4.4.4_08-40.2
SUSE Linux Enterprise Debuginfo 11-SP4 (src):    xen-4.4.4_08-40.2
Comment 15 Andreas Stieger 2016-10-13 15:28:51 UTC 
all done
Comment 16 Swamp Workflow Management 2016-10-13 19:19:20 UTC 
SUSE-SU-2016:2533-1: An update that solves 38 vulnerabilities and has 20 fixes is now available.

Category: security (important)
Bug References: 953339,953362,953518,954872,955399,957986,958848,961600,963161,964427,970135,971949,973188,973631,974038,975130,975138,975907,976058,976111,978164,978295,978413,979035,979620,979670,980716,980724,981264,981276,982024,982025,982026,982224,982225,982286,982695,982960,983973,983984,984981,985503,986586,988675,990843,990923,990970,991934,992224,994421,994625,994761,994772,994775,995785,995789,995792,997731
CVE References: CVE-2014-3615,CVE-2014-3672,CVE-2016-3158,CVE-2016-3159,CVE-2016-3710,CVE-2016-3712,CVE-2016-3960,CVE-2016-4001,CVE-2016-4002,CVE-2016-4020,CVE-2016-4037,CVE-2016-4439,CVE-2016-4441,CVE-2016-4453,CVE-2016-4454,CVE-2016-4480,CVE-2016-4952,CVE-2016-4962,CVE-2016-4963,CVE-2016-5105,CVE-2016-5106,CVE-2016-5107,CVE-2016-5126,CVE-2016-5238,CVE-2016-5337,CVE-2016-5338,CVE-2016-5403,CVE-2016-6258,CVE-2016-6351,CVE-2016-6833,CVE-2016-6834,CVE-2016-6835,CVE-2016-6836,CVE-2016-6888,CVE-2016-7092,CVE-2016-7093,CVE-2016-7094,CVE-2016-7154
Sources used:
SUSE Linux Enterprise Server for SAP 12 (src):    xen-4.4.4_04-22.22.2
SUSE Linux Enterprise Server 12-LTSS (src):    xen-4.4.4_04-22.22.2