CVE-2017-18030 Qemu: Out-of-bounds access in cirrus_invalidate_region routine

[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 refreshing 
vnc surface area, in case the initial pitch was negative in 
cirrus_invalidate_region.

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

Upstream patch:
---------------
  -> https://git.qemu.org/?p=qemu.git;a=commitdiff;h=f153b563f8cf121aebf5a2fff5f0110faf58ccb3

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