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

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Date:   Sat, 25 Feb 2023 20:10:08 +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 25/02/2023 10:14, Eric Dumazet wrote:
> On Sat, Feb 25, 2023 at 8:54 AM Paul Blakey <paulb@...dia.com> wrote:
>>
>>
>>
>> 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.
>>
> 
> The bug I am talking about is triggering because ->net pointer is not
> initialized.
> 
> ->net pointer is initialized in  tcf_exts_init_ex(), before any error
> can be returned.

Right, so all good!