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Message-ID: <c5f1a7bf-b444-4934-a205-3c2b3a045ff7@web.de>
Date: Wed, 3 Jan 2024 17:24:53 +0100
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Subject: Re: [PATCH 1/3] drm: property: One function call less in
 drm_property_create() after error detection
Content-Language: en-GB
To: =?UTF-8?Q?Michel_D=C3=A4nzer?= <michel.daenzer@mailbox.org>,
 dri-devel@lists.freedesktop.org, kernel-janitors@vger.kernel.org,
 Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@gmail.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>
Cc: LKML <linux-kernel@vger.kernel.org>, cocci@inria.fr
References: <ff7ce5d0-59fa-470c-8dd6-68dbe65c18e5@web.de>
 <9b1e7330-f4f6-47f8-a568-eaea1624bb6f@web.de>
 <37647c33-7f9d-4763-8bf4-cfc5c9a811de@mailbox.org>
From: Markus Elfring <Markus.Elfring@web.de>
In-Reply-To: <37647c33-7f9d-4763-8bf4-cfc5c9a811de@mailbox.org>
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 Wahs/w==

>> The kfree() function was called in one case by the
>> drm_property_create() function during error handling
>> even if the passed data structure member contained a null pointer.
>> This issue was detected by using the Coccinelle software.
>>
>> Thus use another label.
=E2=80=A6
>> +++ b/drivers/gpu/drm/drm_property.c
>> @@ -117,7 +117,7 @@ struct drm_property *drm_property_create(struct drm=
_device *dev,
>>  		property->values =3D kcalloc(num_values, sizeof(uint64_t),
>>  					   GFP_KERNEL);
>>  		if (!property->values)
>> -			goto fail;
>> +			goto free_property;
>>  	}
>>
>>  	ret =3D drm_mode_object_add(dev, &property->base, DRM_MODE_OBJECT_PRO=
PERTY);
>> @@ -135,6 +135,7 @@ struct drm_property *drm_property_create(struct drm=
_device *dev,
>>  	return property;
>>  fail:
>>  	kfree(property->values);
>> +free_property:
>>  	kfree(property);
>>  	return NULL;
>>  }
=E2=80=A6
> This change is pointless at best, kfree(NULL) works fine.

* Would you interpret such a special function call as redundant?

* Do you find advices applicable from another information source
  also for this function implementation?
  https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consider+using+a+=
goto+chain+when+leaving+a+function+on+error+when+using+and+releasing+resou=
rces


> Out of curiosity, what exactly did Coccinelle report?

Some SmPL scripts from my own selection tend to point questionable impleme=
ntation details out.

Regards,
Markus