linux-kernel - Re: [PATCH v5 net 2/2] net: udp: fix IP header access and skb lookup on Fast/frag0 UDP GRO

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Date:   Wed, 11 Nov 2020 15:54:45 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alexander Lobakin <alobakin@...me>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 net 2/2] net: udp: fix IP header access and skb lookup
 on Fast/frag0 UDP GRO

On Wed, Nov 11, 2020 at 3:45 PM Alexander Lobakin <alobakin@...me> wrote:
>
> udp{4,6}_lib_lookup_skb() use ip{,v6}_hdr() to get IP header of the
> packet. While it's probably OK for non-frag0 paths, this helpers
> will also point to junk on Fast/frag0 GRO when all headers are
> located in frags. As a result, sk/skb lookup may fail or give wrong
> results. To support both GRO modes, skb_gro_network_header() might
> be used. To not modify original functions, add private versions of
> udp{4,6}_lib_lookup_skb() only to perform correct sk lookups on GRO.
>
> Present since the introduction of "application-level" UDP GRO
> in 4.7-rc1.
>
> Misc: replace totally unneeded ternaries with plain ifs.
>
> Fixes: a6024562ffd7 ("udp: Add GRO functions to UDP socket")
> Suggested-by: Willem de Bruijn <willemb@...gle.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Alexander Lobakin <alobakin@...me>

Acked-by: Willem de Bruijn <willemb@...gle.com>