netdev - Re: [PATCH] net-fq: Add WARN

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Message-ID: <6dd70f92-f026-0b2a-9aed-91f303ee4335@candelatech.com>
Date:   Thu, 7 Jun 2018 14:41:55 -0700
From:   Ben Greear <greearb@...delatech.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] net-fq: Add WARN_ON check for null flow.

On 06/07/2018 02:29 PM, Cong Wang wrote:
> On Thu, Jun 7, 2018 at 9:06 AM,  <greearb@...delatech.com> wrote:
>> --- a/include/net/fq_impl.h
>> +++ b/include/net/fq_impl.h
>> @@ -80,6 +80,9 @@ static struct sk_buff *fq_tin_dequeue(struct fq *fq,
>>
>>         flow = list_first_entry(head, struct fq_flow, flowchain);
>>
>> +       if (WARN_ON_ONCE(!flow))
>> +               return NULL;
>> +
>
> How could even possibly list_first_entry() returns NULL?
> You need list_first_entry_or_null().
>

I don't know for certain flow as null, but something was NULL in this method
near that line and it looked like a likely culprit.

I guess possibly tin or fq was passed in as NULL?

Anyway, if the patch seems worthless just ignore it.  I'll leave it in my tree
since it should be harmless and will let you know if I ever hit it.

If someone else hits a similar crash, hopefully they can report it.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com