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

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Date: Wed, 20 Mar 2024 08:32:17 +0100 (CET)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Dan Carpenter <dan.carpenter@...aro.org>
cc: Jakub Kicinski <kuba@...nel.org>, 
    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, 
    Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers



On Wed, 20 Mar 2024, Dan Carpenter wrote:

> 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.

My understanding from Jonathan Cameron was that Linus wants a NULL always,
unless there is an initialization with the declaration.

julia