$NetBSD: patch-CVE-2016-7909,v 1.1 2016/10/30 14:48:00 spz Exp $

from:
https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg07942.html

From: Prasad J Pandit <address@hidden>

The AMD PC-Net II emulator has set of control and status(CSR)
registers. Of these, CSR76 and CSR78 hold receive and transmit
descriptor ring length respectively. This ring length could range
from 1 to 65535. Setting ring length to zero leads to an infinite
loop in pcnet_rdra_addr. Add check to avoid it.

Reported-by: Li Qiang <address@hidden>

--- hw/net/pcnet.c.orig	2016-09-02 15:34:19.000000000 +0000
+++ hw/net/pcnet.c
@@ -1429,8 +1429,11 @@ static void pcnet_csr_writew(PCNetState 
     case 47: /* POLLINT */
     case 72:
     case 74:
+        break;
     case 76: /* RCVRL */
     case 78: /* XMTRL */
+        val = (val > 0) ? val : 512;
+        break;
     case 112:
        if (CSR_STOP(s) || CSR_SPND(s))
            break;
