CVE-2016-4440 Kernel: kvm: vmx: incorrect state update leading to MSR access

[P J P <ppandit () redhat com>]

  Hello,

Linux kernel built with the Kernel-based virtual machine(CONFIG_KVM) along 
with Hyper-v Synthetic Interrupt Controller(SynIC) support is vulnerable to an 
undue APIC register access issue. In that a guest with SynIC enabled, could 
gain access to host's Machine Specific Registers(MSR).

A privileged user inside guest could use this flaw to crash the host kernel 
resulting in DoS OR potentially leverage it to escalate privileges on the 
host.

Upstream patch:
---------------
  -> http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/152191

Reference:
----------
  -> https://bugzilla.redhat.com/show_bug.cgi?id=1337806
  -> http://comments.gmane.org/gmane.comp.emulators.kvm.devel/152100

'CVE-2016-4440' has been assigned to this issue by Red Hat Inc.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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