CVE-2016-5412 Kernel: powerpc: kvm: Infinite loop via H_CEDE hypercall when running under hypervisor-mode

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

  Hello,

Linux kernel built with for the PowerPC platform with KVM Virtualisation with 
hypervisor-mode support(CONFIG_KVM_BOOK3S_64_HV) enabled is vulnerable to a 
DoS issue. It could occur if a guest kernel running under hypervisor-mode KVM 
(i.e. "HV KVM" rather than "PR KVM"), does the H_CEDE hypercall while a 
suspended transaction exists, the host CPU may, under certain circumstances, 
hang in an infinite loop with interrupts disabled.

A user/process inside guest could use this flaw to crash the host kernel 
resulting in DoS.

Upstream patches:
-----------------
  -> https://marc.info/?l=kvm&m=146968629127349&w=2

Reference:
----------
  -> https://bugzilla.redhat.com/show_bug.cgi?id=1349916


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