Re: [PATCH] net: fix setting csum_start in skb_segment()

From: Tom Herbert
Date: Wed Jun 25 2014 - 22:16:00 EST


On Wed, Jun 25, 2014 at 12:51 PM, Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> From: Tom Herbert <therbert@xxxxxxxxxx>
>
> 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.
>
Acked-by: Tom Herbert <therbert@xxxxxxxxxx>

> Reported-by: Dave Jones <davej@xxxxxxxxxx>
> Tested-by: Dave Jones <davej@xxxxxxxxxx>
> Signed-off-by: Tom Herbert <therbert@xxxxxxxxxx>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Fixes: 7e2b10c1e52ca ("net: Support for multiple checksums with gso")
> ---
> net/core/skbuff.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> 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;
> }
>
>
>
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