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

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Date: Thu, 21 Mar 2024 16:20:09 -0400
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: Markus Elfring <Markus.Elfring@....de>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Dan Carpenter <dan.carpenter@...aro.org>, kernel-janitors@...r.kernel.org,
 netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Tony Nguyen <anthony.l.nguyen@...el.com>,
 LKML <linux-kernel@...r.kernel.org>,
 Alexander Lobakin <aleksander.lobakin@...el.com>,
 David Laight <David.Laight@...lab.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Jesse Brandeburg <jesse.brandeburg@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Jonathan Cameron <jic23@...nel.org>,
 Kees Cook <keescook@...omium.org>,
 Lukasz Czapnik <lukasz.czapnik@...el.com>, Paolo Abeni <pabeni@...hat.com>,
 Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com>
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers

Does one prefer an initialization of null at the top of the function or an initialization to a meaningful value in the middle of the function ?

(Sorry for top posting)

Sent from my iPhone

> On 21 Mar 2024, at 14:14, Markus Elfring <Markus.Elfring@....de> wrote:
> 
> 
>> 
>>> How do you think about to reduce the scope for the affected local variable instead
>>> with the help of a small script (like the following) for the semantic patch language?
>>> 
>>> @movement@
>>> attribute name __free;
>>> @@
>>> -u8 *tx_frame __free(kfree);
>>> int i;
>>> ... when any
>>> if (ice_fltr_add_mac(test_vsi, ...))
>>> { ... }
>>> +
>>> +{
>>> +u8 *tx_frame __free(kfree) = NULL;
>>> if (ice_lbtest_create_frame(pf, &tx_frame, ...))
>>> { ... }
>>> ... when any
>>> +}
>>> +
>>> valid_frames = ice_lbtest_receive_frames(...);
>> 
>> I believe you don't understand what the scope of the above can be.
> 
> Will the understanding improve for the proposed source code transformation?
> 
> Regards,
> Markus