CVE-2019-14821 Kernel: KVM: OOB memory access via mmio ring buffer

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

  Hello,

An out-of-bounds access issue was found in the way Linux kernel's KVM 
hypervisor implements Coalesced MMIO write operation. It operates on a MMIO 
ring buffer 'struct kvm_coalesced_mmio' object, wherein write indices 
'ring->first' and 'ring->last' value could be supplied by a host user-space 
process.

An unprivileged host user/process with access to '/dev/kvm' device could use 
this flaw to crash the host kernel resulting in DoS OR potentially escalate 
privileges on the system.

Upstream patch:
---------------
  -> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=b60fe990c6b07ef6d4df67bc0530c7c90a62623a

This issue was reported by Matt Delco of Google Inc.

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