linux-kernel - Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop

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Date:   Fri, 15 Sep 2023 14:55:08 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Ma Ke <make_ruc2021@....com>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop

On Fri, Sep 15, 2023 at 12:42 PM Ma Ke <make_ruc2021@....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@....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 = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
>         fl = rcu_dereference_bh(q->filter_list);
>         result = tcf_classify(skb, NULL, fl, &res, false);
> +       if (result == TC_ACT_SHOT)
> +               return NULL;
>         if (result >= 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 fine
at line 320 ?