CVE-2018-10853 kernel: kvm: guest userspace to guest kernel write

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

  Hello,

A flaw was found in the way Linux kernel KVM hypervisor emulated instructions 
such as sgdt/sidt/fxsave/fxrstor. It did not check current privilege(CPL) 
level while emulating unprivileged instructions.

An unprivileged guest user/process could use this flaw to potentially escalate 
privileges inside guest.

Upstream patch:
  -> https://git.kernel.org/linus/3c9fa24ca7c9c47605672916491f79e8ccacb9e6

Issue introduced in: (kernel v4.10+)
  -> https://git.kernel.org/linus/129a72a0d3c8e139a04512325384fe5ac119e74

This issue was reported by Andy Lutomirski and Mika Penttilä. CVE-2018-10853 
assigned by Red Hat Inc.

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