netdev - Re: [PATCH v3 net 1/2] dccp/tcp: Avoid negative sk_forward_alloc by ipv6

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Message-ID: <CANn89iLYARLgLrwAMFEHr7g9M1GE7JUfi8OR0yowfwGBqZXtKg@mail.gmail.com>
Date:   Fri, 10 Feb 2023 15:12:13 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
        Andrii <tulup@...l.ru>,
        Arnaldo Carvalho de Melo <acme@...driva.com>
Subject: Re: [PATCH v3 net 1/2] dccp/tcp: Avoid negative sk_forward_alloc by ipv6_pinfo.pktoptions.

On Fri, Feb 10, 2023 at 1:22 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> Eric Dumazet pointed out [0] that when we call skb_set_owner_r()
> for ipv6_pinfo.pktoptions, sk_rmem_schedule() has not been called,
> resulting in a negative sk_forward_alloc.
>
> We add a new helper which clones a skb and sets its owner only
> when sk_rmem_schedule() succeeds.
>
> Note that we move skb_set_owner_r() forward in (dccp|tcp)_v6_do_rcv()
> because tcp_send_synack() can make sk_forward_alloc negative before
> ipv6_opt_accepted() in the crossed SYN-ACK or self-connect() cases.
>
> [0]: https://lore.kernel.org/netdev/CANn89iK9oc20Jdi_41jb9URdF210r7d1Y-+uypbMSbOfY6jqrg@mail.gmail.com/
>
> Fixes: 323fbd0edf3f ("net: dccp: Add handling of IPV6_PKTOPTIONS to dccp_v6_do_rcv()")
> Fixes: 3df80d9320bc ("[DCCP]: Introduce DCCPv6")
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>


Reviewed-by: Eric Dumazet <edumazet@...gle.com>

Thanks !