CVE-2014-8106 qemu: cirrus: insufficient blit region checks

[Petr Matousek <pmatouse () redhat com>]

It was found that the Cirrus blit region checks were insufficient.

Cirrus is the default graphical adapter for x86 in qemu in any released
version, and it's also used for vnc (spice uses qxl).

A privileged guest user could use this flaw to to write outside of vram
allocated buffer boundaries in the host's qemu process with attacker
provided data.

Upstream patch submission:
http://lists.gnu.org/archive/html/qemu-devel/2014-12/msg00508.html

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1169454

-- 
Petr Matousek / Red Hat Product Security
PGP: 0xC44977CA 8107 AF16 A416 F9AF 18F3  D874 3E78 6F42 C449 77CA