linux-kernel - Re: [PATCH] tegra_wm9712: Fix a memory leaking bug in tegra_wm9712_driver

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Date:   Fri, 24 May 2019 15:47:34 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Gen Zhang <blackgod016574@...il.com>
CC:     <lgirdwood@...il.com>, <perex@...ex.cz>,
        <alsa-devel@...a-project.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tegra_wm9712: Fix a memory leaking bug in
 tegra_wm9712_driver_probe()


On 24/05/2019 15:33, Gen Zhang wrote:
> On Fri, May 24, 2019 at 09:33:13AM +0100, Jon Hunter wrote:
>>
>> On 24/05/2019 01:50, Gen Zhang wrote:
>>> In tegra_wm9712_driver_probe(), 'machine->codec' is allocated by
>>> platform_device_alloc(). When it is NULL, function returns ENOMEM.
>>> However, 'machine' is allocated by devm_kzalloc() before this site.
>>> Thus we should free 'machine' before function ends to prevent memory
>>> leaking.
>>
>> Memory allocated by devm_xxx() is automatically freed on failure so this
>> is not correct.
> Thanks for your comments, Jon. But after I examined the code, I am still
> confused about the usage of devm_kmalloc(). You can kindly refer to 
> hisi_sas_debugfs_init() in drivers/scsi/hisi_sas/hisi_sas_main.c. And
> devm_kfree() is used to free a memory allocated by devm_kmalloc(). And
> I found other situations similar to this in other files.
> 
> So, I hope you can give me some guidance on this. Thanks!

Please refer to the devres documentation [0].

Cheers,
Jon

[0] https://www.kernel.org/doc/Documentation/driver-model/devres.txt

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