CVE-2017-2615 Qemu: display: cirrus: oob access while doing bitblt copy backward mode

[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 copying VGA 
data via bitblt copy in backward mode.

A privileged user inside guest could use this flaw to crash the Qemu process 
resulting in DoS OR potentially execute arbitrary code on the host with 
privileges of Qemu process on the host.

Upstream patch
--------------
  -> https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg00015.html

It fixes
  -> http://git.qemu.org/?p=qemu.git;a=commit;h=d3532a0db02296e687711b8cdc7791924efccea0

Reference:
----------
  -> https://bugzilla.redhat.com/show_bug.cgi?id=1418200

This issue was reported by Li Qiang of 360.cn Inc.

CVE-2017-2615 was assigned to this issue by Red Hat Inc.

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