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From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 15 Sep 2023 14:55:08 +0200
Message-ID: <CANn89iJyktWcztc76Pw16MP-k-DfSjstW+WFgRxwUat7p25CGw@mail.gmail.com>
Subject: Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop
To:     Ma Ke <make_ruc2021@163.com>
Cc:     jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
        davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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On Fri, Sep 15, 2023 at 12:42=E2=80=AFPM Ma Ke <make_ruc2021@163.com> wrote=
:
>
> If asked to drop a packet via TC_ACT_SHOT it is unsafe to
> assume res.class contains a valid pointer.
>
> Signed-off-by: Ma Ke <make_ruc2021@163.com>
> ---
>  net/sched/sch_drr.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
> index 19901e77cd3b..2b854cb6edf9 100644
> --- a/net/sched/sch_drr.c
> +++ b/net/sched/sch_drr.c
> @@ -309,6 +309,8 @@ static struct drr_class *drr_classify(struct sk_buff =
*skb, struct Qdisc *sch,
>         *qerr =3D NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
>         fl =3D rcu_dereference_bh(q->filter_list);
>         result =3D tcf_classify(skb, NULL, fl, &res, false);
> +       if (result =3D=3D TC_ACT_SHOT)
> +               return NULL;
>         if (result >=3D 0) {
>  #ifdef CONFIG_NET_CLS_ACT
>                 switch (result) {
> --
> 2.37.2
>

 I do not see a bug, TC_ACT_SHOT is handled in the switch (result) just fin=
e
at line 320 ?