oss-security - Xen Security Advisory 277 v2 - x86: incorrect error handling for guest p2m page removals

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <E1gP62s-0000dz-Ff@xenbits.xenproject.org>
Date: Tue, 20 Nov 2018 13:26:26 +0000
From: Xen.org security team <security@....org>
To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org,
 xen-users@...ts.xen.org, oss-security@...ts.openwall.com
CC: Xen.org security team <security-team-members@....org>
Subject: Xen Security Advisory 277 v2 - x86: incorrect error handling for
 guest p2m page removals

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

                    Xen Security Advisory XSA-277
                              version 2

       x86: incorrect error handling for guest p2m page removals

UPDATES IN VERSION 2
====================

Public release.

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

The internal function querying a domain's p2m table grabs the p2m lock
by default, so that the answer to the query remains true until the
caller can act on that information; it is up to the caller then to
release the lock.  Unfortunately, certain failure paths don't release
the lock.

IMPACT
======

A malicious or buggy guest may cause a deadlock, resulting in a DoS
(Denial of Service) affecting the entire host.

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

Xen 4.11 and onward are vulnerable.

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

Only systems running untrusted HVM or PVH guests are vulnerable.
Systems running only PV guests are not vulnerable.

MITIGATION
==========

Running only PV guests will avoid this vulnerability.

CREDITS
=======

This issue was discovered by Paul Durrant of Citrix.

RESOLUTION
==========

Applying the appropriate attached patch resolves this issue.

xsa277.patch           xen-unstable, Xen 4.11.x

$ sha256sum xsa277*
576cdc05975e43698624b88f7290119dd702b3db8f30f3219754d992d7fef0c6  xsa277.meta
c9025e1daaec4081a61f1ed7b96e69cfe8e35bdd5b4fcc0fadc98f71c2e243e2  xsa277.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
-----BEGIN PGP SIGNATURE-----

iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAlv0C2kMHHBncEB4ZW4u
b3JnAAoJEIP+FMlX6CvZ3W4H/0lfQ3hxNjmYa9soWCkXCFWrRHEt5G11dtL3GE1B
E4GbiAWdownHQjhA3okO9yQKDzwY68+hvVZ7YOUNSQ00tZ8j/RWldDZLhbp9JrjI
QMriPefk8X6ZVnF6velUZI2dpOIX6NFBZHxPXUKV8A+e9/+OS7e9CEWrSaprHcbt
MTHv5evulxl8sPXyVa8e2m2YSdEFU6ylfVyH3m5u3cKBpvbSLFKyQN+MNX8rTmAn
+ga3Vj9zehIlDl22nTXCcQHbj75JK0RsDCcH1Glicqm3LZlZ2GXYNe/OiPdLTmwP
8UN8HJhDB2d6w8x4/TV2ad8UGqCJghkxJkqs2RJJdtz8VSo=
=CFtL
-----END PGP SIGNATURE-----

Download attachment "xsa277.meta" of type "application/octet-stream" (666 bytes)

Download attachment "xsa277.patch" of type "application/octet-stream" (1835 bytes)

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.