linux-kernel - Re: [PATCH] net: dccp: delete redundant ackvec record in dccp_insert

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Message-ID: <CANn89iJmYoewECcRTDW-F5c=jJZRxwFGMMrOGYe6XBLOgohc6w@mail.gmail.com>
Date:   Tue, 21 Feb 2023 13:46:36 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        ian.mcdonald@...di.co.nz, gerrit@....abdn.ac.uk,
        dccp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dccp: delete redundant ackvec record in dccp_insert_options()

On Tue, Feb 21, 2023 at 10:22 AM Hangyu Hua <hbh25y@...il.com> wrote:
>
> A useless record can be insert into av_records when dccp_insert_options()
> fails after dccp_insert_option_ackvec(). Repeated triggering may cause
> av_records to have a lot of useless record with the same avr_ack_seqno.
>
> Fixes: 8b7b6c75c638 ("dccp: Integrate feature-negotiation insertion code")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---
>  net/dccp/options.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/net/dccp/options.c b/net/dccp/options.c
> index d24cad05001e..8aa4abeb15ea 100644
> --- a/net/dccp/options.c
> +++ b/net/dccp/options.c
> @@ -549,6 +549,8 @@ static void dccp_insert_option_padding(struct sk_buff *skb)
>  int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
>  {
>         struct dccp_sock *dp = dccp_sk(sk);
> +       struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
> +       struct dccp_ackvec_record *avr;
>
>         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
>
> @@ -577,16 +579,22 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
>
>         if (dp->dccps_hc_rx_insert_options) {
>                 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
> -                       return -1;
> +                       goto delete_ackvec;
>                 dp->dccps_hc_rx_insert_options = 0;
>         }
>
>         if (dp->dccps_timestamp_echo != 0 &&
>             dccp_insert_option_timestamp_echo(dp, NULL, skb))
> -               return -1;
> +               goto delete_ackvec;
>
>         dccp_insert_option_padding(skb);
>         return 0;
> +
> +delete_ackvec:
> +       avr = dccp_ackvec_lookup(&av->av_records, DCCP_SKB_CB(skb)->dccpd_seq);

Why avr would be not NULL ?

> +       list_del(&avr->avr_node);
> +       kmem_cache_free(dccp_ackvec_record_slab, avr);
> +       return -1;
>  }

Are you really using DCCP and/or how have you tested this patch ?

net/dccp/ackvec.c:15:static struct kmem_cache *dccp_ackvec_record_slab;

I doubt this patch has been compiled.

I would rather mark DCCP deprecated and stop trying to fix it.