linux-kernel - Re: [PATCH net] net: ethernet: adi: adin1110: Fix some error handling path in adin1110_read

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Message-ID: <bf75a318-a3e1-4d03-85f3-63b316b22346@wanadoo.fr>
Date: Fri, 4 Oct 2024 15:27:35 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Lennart Franzen <lennart@...omain.com>,
 Alexandru Tachici <alexandru.tachici@...log.com>,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net] net: ethernet: adi: adin1110: Fix some error handling
 path in adin1110_read_fifo()

Le 04/10/2024 à 13:47, Dan Carpenter a écrit :
> On Thu, Oct 03, 2024 at 08:53:15PM +0200, Christophe JAILLET wrote:
>> If 'frame_size' is too small or if 'round_len' is an error code, it is
>> likely that an error code should be returned to the caller.
>>
>> Actually, 'ret' is likely to be 0, so if one of these sanity checks fails,
>> 'success' is returned.
>>
>> Return -EINVAL instead.
>>
>> Fixes: bc93e19d088b ("net: ethernet: adi: Add ADIN1110 support")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>> This patch is speculative.
>> If returning 0 is what was intended, then an explicit 0 would be better.
> 
> I have an unpublished Smatch warning for these:
> 
> drivers/net/ethernet/adi/adin1110.c:321 adin1110_read_fifo() info: returning a literal zero is cleaner
> drivers/net/ethernet/adi/adin1110.c:325 adin1110_read_fifo() info: returning a literal zero is cleaner
> 
> It's a pity that deliberately doing a "return ret;" when ret is zero is so
> common.  Someone explained to me that it was "done deliberately to express that
> we were propagating the success from frob_whatever()".  No no no!
> 
> I don't review these warnings unless I'm fixing a bug in the driver because
> they're too common.  The only ones I review are:
> 
> 	ret = frob();
> 	if (!ret)
> 		return ret;
> 
> Maybe 20% of the time those warnings indicate a reversed if statement.
> 
> Your heuristic here is very clever and I'll try steal it to create a new more
> specific warning.

Well my heuristic is mostly luck, here ;-)

Anyway, what I was looking for (un-initialized last argument in some 
function) could be nice to have in smatch, if not already present.

Finally, if you want, I can give a look at the warnings if you share the 
log.

CJ

> 
> regards,
> dan carpenter
> 
> 
>