Xen.org security team
2012-Sep-05 09:38 UTC
Xen Security Advisory 12 (CVE-2012-3494) - hypercall set_debugreg vulnerability
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Xen Security Advisory CVE-2012-3494 / XSA-12
version 3
hypercall set_debugreg vulnerability
UPDATES IN VERSION 3
===================
Public release.
ISSUE DESCRIPTION
================
set_debugreg allows writes to reserved bits of the DR7 debug control
register on x86-64.
IMPACT
=====
A malicious guest can cause the host to crash, leading to a DoS.
If the vulnerable hypervisor is run on future hardware, the impact of
the vulnerability might be widened depending on the future assignment
of the currently-reserved debug register bits.
VULNERABLE SYSTEMS
=================
All systems running 64-bit paravirtualised guests.
The vulnerability dates back to at least Xen 4.0. 4.0, 4.1, the 4.2
RCs, and xen-unstable.hg are all vulnerable.
MITIGATION
=========
This issue can be mitigated by ensuring (inside the guest) that the
kernel is trustworthy, or by running only 32-bit or HVM guests.
RESOLUTION
=========
Applying the appropriate attached patch will resolve the issue.
PATCH INFORMATION
================
The attached patch resolves this issue:
Xen unstable, 4.1 and 4.0 xsa12-all.patch
$ sha256sum xsa12-all.patch
2415ee133e28b1c848c5ae3ce766cc2a67009bad8d026879030a6511b85dbc13
xsa12-all.patch
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