CVE-2015-5279 Qemu: net: add checks to validate ring buffer pointers

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

  Hello,

Qemu emulator built with the NE2000 NIC emulation support is vulnerable to a 
heap buffer overflow issue. It could occur when receiving packets over the 
network.

A privileged user inside guest could use this flaw to crash the Qemu instance 
or potentially execute arbitrary code on the host.

Upstream fix:
-------------
  -> https://lists.gnu.org/archive/html/qemu-devel/2015-09/msg03984.html


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