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

When decoding a guest write to a specific register in the virtual
interrupt controller Xen would treat an invalid value as a critical
error and crash the host.

IMPACT
======

By writing an invalid value to the GICD.SGIR register a guest can
crash the host, resulting in a Denial of Service attack.

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

Xen 4.5 and later systems running on ARM hardware with version 2 of
the generic interrupt controller are vulnerable.

Systems running on ARM hardware with version 3 of the generic
interrupt controller are not vulnerable.

x86 systems are not affected.

Statement:

This issue did not affect the versions of xen as shipped with Red Hat Enterprise Linux 5.

Acknowledgements:

Red Hat would like to thank the Xen project for reporting this issue.