Re: [PATCH net] net: drop bad gso csum_start and offset in virtio_net_hdr

[Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>]

On Fri, Jul 26, 2024 at 3:00 AM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Fri, Jul 26, 2024 at 4:34 AM Willem de Bruijn
> <willemdebruijn.kernel@xxxxxxxxx> wrote:
> >
> > From: Willem de Bruijn <willemb@xxxxxxxxxx>
>
> ...
>
> >                 /* Kernel has a special handling for GSO_BY_FRAGS. */
> > diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> > index 4b791e74529e1..9e49ffcc77071 100644
> > --- a/net/ipv4/tcp_offload.c
> > +++ b/net/ipv4/tcp_offload.c
> > @@ -140,6 +140,9 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
> >         if (thlen < sizeof(*th))
> >                 goto out;
> >
> > +       if (unlikely(skb->csum_start != skb->transport_header))
> > +               goto out;
> > +
>
> Using skb_transport_header() will make sure DEBUG_NET_WARN_ON_ONCE()
> will fire for debug kernels,
> with no additional costs for non debug kernels (compiler will generate
> not use skb->head at all)
>
> if (unlikely(skb->csum_start != skb_transport_header(skb) - skb->head))
>                   goto out;
>
> (This will match the corresponding initialization in __tcp_v4_send_check())

Will do, thanks.