netdev - Re: [PATCH net] ice: Fix freeing uninitialized pointers

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Date: Wed, 20 Mar 2024 08:01:49 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers

On Tue, Mar 19, 2024 at 12:43:17PM -0700, Jakub Kicinski wrote:
> On Sat, 16 Mar 2024 12:44:40 +0300 Dan Carpenter wrote:
> > -	struct ice_aqc_get_phy_caps_data *pcaps __free(kfree);
> > -	void *mac_buf __free(kfree);
> > +	struct ice_aqc_get_phy_caps_data *pcaps __free(kfree) = NULL;
> > +	void *mac_buf __free(kfree) = NULL;
> 
> This is just trading one kind of bug for another, and the __free()
> magic is at a cost of readability.
> 
> I think we should ban the use of __free() in all of networking,
> until / unless it cleanly handles the NULL init case.

Free handles the NULL init case, it doesn't handle the uninitialized
case.  I had previously argued that checkpatch should complain about
every __free() pointer if the declaration doesn't have an assignment.

The = NULL assignment is unnecessary if the pointer is assigned to
something else before the first return, so this might cause "unused
assignment" warnings?  I don't know if there are any tools which
complain about that in that situation.  I think probably we should just
make that an exception and do the checkpatch thing because it's such a
simple rule to implement.

regards,
dan carpenter