From 305025fe1852b99fcd84b6cd75ed7392d4f49efc Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Fri, 31 Jul 2015 15:59:44 +0200
Subject: [PATCH 3/7] rtl8139: skip offload on short Ethernet/IP header
 (CVE-2015-5165)

Message-id: <1438358388-10575-4-git-send-email-stefanha@redhat.com>
Patchwork-id: 67237
O-Subject: [RHEL-7.1.z qemu-kvm EMBARGOED PATCH 3/7] rtl8139: skip offload on short Ethernet/IP header (CVE-2015-5165)
Bugzilla: 1248764
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Xiao Wang <jasowang@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

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: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/net/rtl8139.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index ab32714..409029d 100644
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -2142,6 +2142,11 @@ 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;
-- 
1.8.3.1