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Subject: Re: [PATCH] tegra_wm9712: Fix a memory leaking bug in
 tegra_wm9712_driver_probe()
To:     Gen Zhang <blackgod016574@gmail.com>
CC:     <lgirdwood@gmail.com>, <perex@perex.cz>,
        <alsa-devel@alsa-project.org>, <linux-tegra@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20190524005014.GA2289@zhanggen-UX430UQ>
 <b2d43dfe-17e5-a975-435b-49f2aa2ad550@nvidia.com>
 <20190524143309.GA8631@zhanggen-UX430UQ>
From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <e52f4140-a119-a584-40a2-6359d6e1784a@nvidia.com>
Date:   Fri, 24 May 2019 15:47:34 +0100
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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

-- 
nvpublic