netdev - Re: [PATCH net-next v13 3/8] net/sched: flower: Move filter handle initialization earlier

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Message-ID: <083dceba-cc14-5aaf-1661-0ce5e29f161a@nvidia.com>
Date:   Sat, 25 Feb 2023 09:53:50 +0200
From:   Paul Blakey <paulb@...dia.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     netdev@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Oz Shlomo <ozsh@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        Roi Dayan <roid@...dia.com>, Vlad Buslov <vladbu@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v13 3/8] net/sched: flower: Move filter handle
 initialization earlier



On 23/02/2023 12:24, Eric Dumazet wrote:
> On Fri, Feb 17, 2023 at 11:36 PM Paul Blakey <paulb@...dia.com> wrote:
>>
>> To support miss to action during hardware offload the filter's
>> handle is needed when setting up the actions (tcf_exts_init()),
>> and before offloading.
>>
>> Move filter handle initialization earlier.
>>
>> Signed-off-by: Paul Blakey <paulb@...dia.com>
>> Reviewed-by: Jiri Pirko <jiri@...dia.com>
>> Reviewed-by: Simon Horman <simon.horman@...igine.com>
>> Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
>> ---
> 
> Error path is now potentially crashing because net pointer has not
> been initialized.
> 
> I plan fixing this issue with the following:
> 
> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> index e960a46b05205bb0bca7dc0d21531e4d6a3853e3..475fe222a85566639bac75fc4a95bf649a10357d
> 100644
> --- a/net/sched/cls_flower.c
> +++ b/net/sched/cls_flower.c
> @@ -2200,8 +2200,9 @@ static int fl_change(struct net *net, struct
> sk_buff *in_skb,
>                  fnew->flags = nla_get_u32(tb[TCA_FLOWER_FLAGS]);
> 
>                  if (!tc_flags_valid(fnew->flags)) {
> +                       kfree(fnew);
>                          err = -EINVAL;
> -                       goto errout;
> +                       goto errout_tb;
>                  }
>          }
> 
> @@ -2226,8 +2227,10 @@ static int fl_change(struct net *net, struct
> sk_buff *in_skb,
>                  }
>                  spin_unlock(&tp->lock);
> 
> -               if (err)
> -                       goto errout;
> +               if (err) {
> +                       kfree(fnew);
> +                       goto errout_tb;
> +               }
>          }
>          fnew->handle = handle;
> 
> @@ -2337,7 +2340,6 @@ static int fl_change(struct net *net, struct
> sk_buff *in_skb,
>          fl_mask_put(head, fnew->mask);
>   errout_idr:
>          idr_remove(&head->handle_idr, fnew->handle);
> -errout:
>          __fl_put(fnew);
>   errout_tb:
>          kfree(tb);


Notice that the bug was before this patch as well.
We init exts->net only in  fl_set_parms()->tcf_exts_validate(exts), and 
before this patch we called __fl_put() on two errors before that (like 
if tcf_exts_init() failed).


Here, its the same, we can't call __fl_put(fnew) till we called 
fl_set_parms(). So you're missing this "goto errorout_idr":


	err = tcf_exts_init_ex(&fnew->exts, net, TCA_FLOWER_ACT, 0, tp, handle, 
!tc_skip_hw(fnew->flags));
	if (err < 0)
		goto errout_idr;

Thanks,
Paul.