Xen.org security team
2012-Aug-09 15:02 UTC
Xen Security Advisory 11 (CVE-2012-3433) - HVM destroy p2m host DoS
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Xen Security Advisory CVE-2012-3433 / XSA-11
version 3
HVM guest destroy p2m teardown host DoS vulnerability
UPDATES IN VERSION 3
===================
Embargo ended Thursday 2012-08-09 12:00:00 UTC.
ISSUE DESCRIPTION
================
An HVM guest is able to manipulate its physical address space such
that tearing down the guest takes an extended period amount of
time searching for shared pages.
This causes the domain 0 VCPU which tears down the domain to be
blocked in the destroy hypercall. This causes that domain 0 VCPU to
become unavailable and may cause the domain 0 kernel to panic.
There is no requirement for memory sharing to be in use.
IMPACT
=====
A guest kernel can cause the host to become unresponsive for a period
of time, potentially leading to a DoS.
VULNERABLE SYSTEMS
=================
All systems running HVM guests with untrusted guest kernels.
This vulnerability effects only Xen 4.0 and 4.1. Xen 3.4 and earlier
and xen-unstable are not vulnerable.
MITIGATION
=========
This issue can be mitigated by running PV (para-virtualised) guests
only, or by ensuring (inside the guest) that the kernel is
trustworthy.
RESOLUTION
=========
Applying the appropriate attached patch will resolve the issue.
NOTE REGARDING CVE
=================
We do not yet have a CVE Candidate number for this vulnerability.
PATCH INFORMATION
================
The attached patches resolve this issue
Xen 4.1, 4.1.x xsa11-4.1.patch
Xen 4.0, 4.0.x xsa11-4.0.patch
$ sha256sum xsa11-*.patch
c8ab767d831b20a1b22c69a28127303c89cf0379cbf6f1ba3acfda6240aa2a89
xsa11-4.0.patch
61c6424023a26a8b4ea591d0bff6969908091a1a1e1304567d0d910908f21e8d
xsa11-4.1.patch
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