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From 62f1eddbc1e0261ff18e5a0dd0e0db23a93e8d4e Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Fri, 31 Jul 2015 15:59:47 +0200
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Subject: [PATCH 12/13] rtl8139: skip offload on short TCP header
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 (CVE-2015-5165)
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Message-id: <1438358388-10575-7-git-send-email-stefanha@redhat.com>
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Patchwork-id: 67241
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O-Subject: [RHEL-7.1.z qemu-kvm EMBARGOED PATCH 6/7] rtl8139: skip offload on short TCP header (CVE-2015-5165)
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Bugzilla: 1248766
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Xiao Wang <jasowang@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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TCP Large Segment Offload accesses the TCP header in the packet.  If the
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packet is too short we must not attempt to access header fields:
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  tcp_header *p_tcp_hdr = (tcp_header*)(eth_payload_data + hlen);
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  int tcp_hlen = TCP_HEADER_DATA_OFFSET(p_tcp_hdr);
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/net/rtl8139.c | 5 +++++
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 1 file changed, 5 insertions(+)
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diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
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index 61bc34c..c9bf454 100644
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--- a/hw/net/rtl8139.c
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+++ b/hw/net/rtl8139.c
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@@ -2202,6 +2202,11 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
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             if ((txdw0 & CP_TX_LGSEN) && ip_protocol == IP_PROTO_TCP)
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             {
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+                /* Large enough for the TCP header? */
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+                if (ip_data_len < sizeof(tcp_header)) {
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+                    goto skip_offload;
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+                }
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+
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                 int large_send_mss = (txdw0 >> 16) & CP_TC_LGSEN_MSS_MASK;
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                 DPRINTF("+++ C+ mode offloaded task TSO MTU=%d IP data %d "
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-- 
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1.8.3.1
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