qemu: Security fix CVE-2016-4439

qemu: Security fix CVE-2016-4439

affects qemu < 2.7.0

Quick Emulator(Qemu) built with the ESP/NCR53C9x controller emulation
support is vulnerable to an OOB write access issue. The controller uses
16-byte FIFO buffer for command and data transfer. The OOB write occurs
while writing to this command buffer in routine get_cmd().

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

References:
----------
http://www.openwall.com/lists/oss-security/2016/05/19/4
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-4441

Signed-off-by: Adrian Dudau <adrian.dudau@enea.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>