netdev - Re: [Intel-wired-lan] [PATCH net-next 1/2] igc: AF_XDP zero-copy metadata adjust breaks SKBs on XDP

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Message-ID: <66f62ef7-f4c6-08df-a8e1-dbbe34b9b125@redhat.com>
Date:   Fri, 26 Nov 2021 16:32:47 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     brouer@...hat.com, netdev@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, bjorn@...nel.org,
        Jakub Kicinski <kuba@...nel.org>, bpf@...r.kernel.org,
        Daniel Borkmann <borkmann@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>, magnus.karlsson@...el.com
Subject: Re: [Intel-wired-lan] [PATCH net-next 1/2] igc: AF_XDP zero-copy
 metadata adjust breaks SKBs on XDP_PASS



On 26/11/2021 16.25, Maciej Fijalkowski wrote:
> On Mon, Nov 15, 2021 at 09:36:25PM +0100, Jesper Dangaard Brouer wrote:
>> Driver already implicitly supports XDP metadata access in AF_XDP
>> zero-copy mode, as xsk_buff_pool's xp_alloc() naturally set xdp_buff
>> data_meta equal data.
>>
>> This works fine for XDP and AF_XDP, but if a BPF-prog adjust via
>> bpf_xdp_adjust_meta() and choose to call XDP_PASS, then igc function
>> igc_construct_skb_zc() will construct an invalid SKB packet. The
>> function correctly include the xdp->data_meta area in the memcpy, but
>> forgot to pull header to take metasize into account.
>>
>> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
>> Signed-off-by: Jesper Dangaard Brouer<brouer@...hat.com>
> Acked-by: Maciej Fijalkowski<maciej.fijalkowski@...el.com>
> 
> Great catch. Will take a look at other ZC enabled Intel drivers if they
> are affected as well.

Thanks a lot for taking this task!!! :-)
--Jesper