netdev - Re: [Intel-wired-lan] [PATCH net] igc: Fix passing 0 to ERR_PTR in igc_xdp_run

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Message-ID: <e6a69093-3ce0-4189-a0cc-21734feace37@intel.com>
Date: Thu, 17 Oct 2024 09:25:38 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Simon Horman <horms@...nel.org>
CC: Yue Haibing <yuehaibing@...wei.com>, <anthony.l.nguyen@...el.com>,
	<przemyslaw.kitszel@...el.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <ast@...nel.org>,
	<daniel@...earbox.net>, <hawk@...nel.org>, <john.fastabend@...il.com>,
	<vedang.patel@...el.com>, <andre.guedes@...el.com>,
	<maciej.fijalkowski@...el.com>, <jithu.joseph@...el.com>,
	<intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH net] igc: Fix passing 0 to ERR_PTR in
 igc_xdp_run_prog()



On 10/17/2024 7:16 AM, Simon Horman wrote:
> On Wed, Oct 16, 2024 at 04:06:34PM -0700, Jacob Keller wrote:
>>
>> Not quite. PTR_ERR_OR_ZERO is intended for the case where you are
>> extracting an error from a pointer. This is converting an error into a
>> pointer.
> 
> Yes, silly me.
> 
>> I am not sure what is really expected here. If res is zero, shouldn't we
>> be returning an skb pointer and not NULL?
> 
> Right. I think the whole point of the cited warning is that it highlights
> code that is often buggy. I think I may have tried to address it in the
> past, but if so unsuccessfully. In any case, I do think it would be good to
> dig into this and either fix it properly (or understand why it is correct
> and note that somewhere.
> 

Right. I think we identified the correct fix. This same code was in i40e
and was removed in a better way.