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

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Message-ID: <63dbd539-2f94-4b68-ab4e-c49e7b9d2ddd@stanley.mountain>
Date: Fri, 4 Oct 2024 14:47:22 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
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()

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I have an unpublished Smatch warning for these: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.

regards,
dan carpenter