From: Tom Herbert <therbert@google.com>
Date: Wed, 25 Jun 2014 19:51:01 +0000 (-0700)
Subject: net: fix setting csum_start in skb_segment()
X-Git-Tag: firefly_0821_release~176^2~3698^2
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=de843723f9b989178762196fb24dd050cbe20ca3;p=firefly-linux-kernel-4.4.55.git

net: fix setting csum_start in skb_segment()

Dave Jones reported that a crash is occurring in

csum_partial
tcp_gso_segment
inet_gso_segment
? update_dl_migration
skb_mac_gso_segment
__skb_gso_segment
dev_hard_start_xmit
sch_direct_xmit
__dev_queue_xmit
? dev_hard_start_xmit
dev_queue_xmit
ip_finish_output
? ip_output
ip_output
ip_forward_finish
ip_forward
ip_rcv_finish
ip_rcv
__netif_receive_skb_core
? __netif_receive_skb_core
? trace_hardirqs_on
__netif_receive_skb
netif_receive_skb_internal
napi_gro_complete
? napi_gro_complete
dev_gro_receive
? dev_gro_receive
napi_gro_receive

It looks like a likely culprit is that SKB_GSO_CB()->csum_start is
not set correctly when doing non-scatter gather. We are using
offset as opposed to doffset.

Reported-by: Dave Jones <davej@redhat.com>
Tested-by: Dave Jones <davej@redhat.com>
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 7e2b10c1e52ca ("net: Support for multiple checksums with gso")
Acked-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9cd5344fad73..c1a33033cbe2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2993,7 +2993,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 							    skb_put(nskb, len),
 							    len, 0);
 			SKB_GSO_CB(nskb)->csum_start =
-			    skb_headroom(nskb) + offset;
+			    skb_headroom(nskb) + doffset;
 			continue;
 		}