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SYNTHESIS OF THE VULNERABILITY

An attacker located in a PV guest can use XRSTOR, in order to
trigger a denial of service of the Xen hypervisor.

– Impacted products: Unix (platform)
– Severity: 1/4
– Creation date: 04/06/2013

DESCRIPTION OF THE VULNERABILITY

The Floating Point Unit (FPU, x87) is used during floating point
arithmetic operations. The FPU contains 3 debug registers: FOP,
FIP and FDP. The FSAVE/FSTOR or FXSAVE/FXSTOR instructions save
and restore these registers. The support is enabled via the
"xsave" option.

However, Xen does not manage exceptions occurring during the
execution of XRSTOR.

An attacker located in a PV guest can therefore use XRSTOR, in
order to trigger a denial of service of the Xen hypervisor.

ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN

http://vigilance.fr/vulnerability/Xen-denial-of-service-via-XRSTOR-12902