From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Wed, 15 Jul 2015 17:17:00 +0000 (+0100)
Subject: rtl8139: skip offload on short Ethernet/IP header
X-Git-Tag: xen-4.7.0~6
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=8d3ca030c3bea00fa7212518f13cec62f41b4d5e;p=qemu-xen-unstable.git

rtl8139: skip offload on short Ethernet/IP header

Transmit offload features access Ethernet and IP headers the packet.  If
the packet is too short we must not attempt to access header fields:

  int proto = be16_to_cpu(*(uint16_t *)(saved_buffer + 12));
  ...
  eth_payload_data = saved_buffer + ETH_HLEN;
  ...
  ip = (ip_header*)eth_payload_data;
  if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
[Backport to qemu-xen-tradition]
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 8b17bd9d81..75ef9b4039 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -2103,6 +2103,11 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
             #define ETH_HLEN    14
             #define ETH_MTU     1500
 
+            /* Large enough for Ethernet and IP headers? */
+            if (saved_size < ETH_HLEN + sizeof(ip_header)) {
+                goto skip_offload;
+            }
+
             /* ip packet header */
             ip_header *ip = 0;
             int hlen = 0;