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: qemu-xen-4.6.0-rc1~5
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=fa1d29345aa1140d70d4962327f382f9866e6fcb;p=qemu-upstream-4.6-testing.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>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---

diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index 2f12d42fe..d377b6b4b 100644
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -2164,6 +2164,11 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
         {
             DPRINTF("+++ C+ mode offloaded task checksum\n");
 
+            /* Large enough for Ethernet and IP headers? */
+            if (saved_size < ETH_HLEN + sizeof(ip_header)) {
+                goto skip_offload;
+            }
+
             /* ip packet header */
             ip_header *ip = NULL;
             int hlen = 0;