netdev - Re: [PATCH net v2] udp: fix skb_copy_and_csum

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Message-ID: <CAKgT0Ue6YFY-t3KS4avzDFE1hLtC=KVZqOdxLTbnOhk9=hW5KQ@mail.gmail.com>
Date:   Wed, 3 Feb 2021 12:54:21 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, oliver.graute@...il.com,
        Sagi Grimberg <sagi@...mberg.me>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net v2] udp: fix skb_copy_and_csum_datagram with odd
 segment sizes

On Wed, Feb 3, 2021 at 11:29 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> From: Willem de Bruijn <willemb@...gle.com>
>
> When iteratively computing a checksum with csum_block_add, track the
> offset "pos" to correctly rotate in csum_block_add when offset is odd.
>
> The open coded implementation of skb_copy_and_csum_datagram did this.
> With the switch to __skb_datagram_iter calling csum_and_copy_to_iter,
> pos was reinitialized to 0 on each call.
>
> Bring back the pos by passing it along with the csum to the callback.
>
> Changes v1->v2
>   - pass csum value, instead of csump pointer (Alexander Duyck)
>
> Link: https://lore.kernel.org/netdev/20210128152353.GB27281@optiplex/
> Fixes: 950fcaecd5cc ("datagram: consolidate datagram copy to iter helpers")
> Reported-by: Oliver Graute <oliver.graute@...il.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Looks good to me.

Reviewed-by: Alexander Duyck <alexanderduyck@...com>