netdev - Re: [PATCH net] net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag

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Message-ID: <CAKgT0Ufd40gmaW7eLu3sRHd=4CeY9WNmgRBUzNt5_+0tEKEMvA@mail.gmail.com>
Date:   Fri, 6 Sep 2019 08:42:45 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Shmulik Ladkani <shmulik@...anetworks.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>, eyal@...anetworks.com,
        netdev <netdev@...r.kernel.org>,
        Shmulik Ladkani <shmulik.ladkani@...il.com>
Subject: Re: [PATCH net] net: gso: Fix skb_segment splat when splitting
 gso_size mangled skb having linear-headed frag_list

On Fri, Sep 6, 2019 at 8:37 AM Shmulik Ladkani <shmulik@...anetworks.com> wrote:
>
> On Fri, 6 Sep 2019 10:49:55 -0400
> Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
>
> > But I wonder whether it is a given that head_skb has headlen.
>
> This is what I observed for GRO packets that do have headlen frag_list
> members: the 'head_skb' itself had a headlen too, and its head was
> built using the original gso_size (similar to the frag_list members).
>
> Maybe Eric can comment better.
>
> > Btw, it seems slightly odd to me tot test head_frag before testing
> > headlen in the v2 patch.
>
> Requested by Alexander. I'm fine either way.

Yeah, my thought on that was "do we care about the length if the data
is stored in a head_frag?". I suppose you could flip the logic and
make it "do we care about it being a head_frag if there is no data
there?". The reason I had suggested the head_frag test first was
because it was a single test bit whereas the length requires reading
two fields and doing a comparison.

For either ordering it is fine by me. So if we need to feel free to
swap those two tests for a v3.

Reviewed-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>