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

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Date: Wed, 20 Mar 2024 20:29:16 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Dan Carpenter <dan.carpenter@...aro.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 Wed, 20 Mar 2024 08:01:49 +0300 Dan Carpenter wrote:
> > 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.

What I was trying to say is that the __free() thing is supposed to
prevent bugs, and it's not. Even if it was easy to write the matcher
rule, if __free() needs a rule to double check its use - it's failing 
at making it easier to write correct code.

In any case. This is a patch for Intel wired, I'll let Intel folks
decide.