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

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Date: Thu, 28 Jul 2016 17:00:39 +0530 (IST)
From: P J P <ppandit@...hat.com>
To: oss security list <oss-security@...ts.openwall.com>
cc: paulus@....ibm.com, David Gibson <dgibson@...hat.com>
Subject: CVE-2016-5412 Kernel: powerpc: kvm: Infinite loop via H_CEDE hypercall
 when running under hypervisor-mode

   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
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F

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