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>

diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index ff500c2eafb904fd0e20302e2b1de85e52f7da66..53698481bcb553ef532cdb0f04161532e783e04e 100644 (file)
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -2140,6 +2140,11 @@ 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;