netdev - Re: [Patch net-next] net_sched: properly check for empty skb array on error path

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Date:   Mon, 18 Dec 2017 20:54:37 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [Patch net-next] net_sched: properly check for empty skb array on
 error path

On 12/18/2017 08:31 PM, Cong Wang wrote:
> On Mon, Dec 18, 2017 at 7:58 PM, John Fastabend
> <john.fastabend@...il.com> wrote:
>> On 12/18/2017 06:20 PM, Cong Wang wrote:
>>> On Mon, Dec 18, 2017 at 5:25 PM, John Fastabend
>>> <john.fastabend@...il.com> wrote:
>>>> On 12/18/2017 02:34 PM, Cong Wang wrote:
>>>>> First, the check of &q->ring.queue against NULL is wrong, it
>>>>> is always false. We should check the value rather than the address.
>>>>>
>>>>
>>>> Thanks.
>>>>
>>>>> Secondly, we need the same check in pfifo_fast_reset() too,
>>>>> as both ->reset() and ->destroy() are called in qdisc_destroy().
>>>>>
>>>>
>>>> not that it hurts to have the check here, but if init fails
>>>> in qdisc_create it seems only ->destroy() is called without
>>>> a ->reset().
>>>>
>>>> Is there another path for init() to fail that I'm missing.
>>>
>>> Pretty sure ->reset() is called in qdisc_destroy() and also before
>>> ->destroy():
>>>
>>
>> Except, the failed init path does not call qdisc_destroy.
>>
>> static struct Qdisc *qdisc_create(struct net_device *dev,
>> [...]
>>
>>         if (ops->init) {
>>                 err = ops->init(sch, tca[TCA_OPTIONS]);
>>                 if (err != 0)
>>                         goto err_out5;
>>         }
>> [...]
>>
>> err_out5:
>>         /* ops->init() failed, we call ->destroy() like qdisc_create_dflt() */
>>         if (ops->destroy)
>>                 ops->destroy(sch);
> 
> Didn't I say qdisc_destroy() rather than ->destroy()? :-)
> 

Yep, thanks for the fix.

Acked-by: John Fastabend <john.fastabend@...il.com>