CVE-2018-7858 Qemu: cirrus: OOB access when updating vga display

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

  Hello,

Quick emulator(QEMU) built with the Cirrus CLGD 54xx VGA Emulator support is 
vulnerable to an out-of-bounds access issue. It could occur while updating VGA 
display, after guest has adjusted the display dimensions.

A privileged user inside guest could use this flaw to crash the Qemu process 
resulting in DoS.

Upstream patch:
---------------
  -> https://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg02174.html

This issue was reported by Ross Lagerwall of citrix.com.

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