linux-kernel - Re: [PATCH] cpufreq: brcmstb-avs-cpufreq: Fix some resource leaks in the error handling path of the probe function

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Date:   Sun, 27 Dec 2020 18:22:00 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     mmayer@...adcom.com, bcm-kernel-feedback-list@...adcom.com,
        rjw@...ysocki.net, f.fainelli@...il.com, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] cpufreq: brcmstb-avs-cpufreq: Fix some resource leaks in
 the error handling path of the probe function

Le 22/12/2020 à 05:35, Viresh Kumar a écrit :
> On 19-12-20, 11:17, Christophe JAILLET wrote:
>> If 'cpufreq_register_driver()' fails, we must release the resources
>> allocated in 'brcm_avs_prepare_init()' as already done in the remove
>> function.
>>
>> To do that, introduce a new function 'brcm_avs_prepare_uninit()' in order
>> to avoid code duplication. This also makes the code more readable (IMHO).
>>
>> Fixes: de322e085995 ("cpufreq: brcmstb-avs-cpufreq: AVS CPUfreq driver for Broadcom STB SoCs")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>> I'm not sure that the existing error handling in the remove function is
>> correct and/or needed.
>> ---
>>   drivers/cpufreq/brcmstb-avs-cpufreq.c | 25 ++++++++++++++++++++-----
>>   1 file changed, 20 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c
>> index 3e31e5d28b79..750ca7cfccb0 100644
>> --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c
>> +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c
>> @@ -597,6 +597,16 @@ static int brcm_avs_prepare_init(struct platform_device *pdev)
>>   	return ret;
>>   }
>>   
>> +static void brcm_avs_prepare_uninit(struct platform_device *pdev)
>> +{
>> +	struct private_data *priv;
>> +
>> +	priv = platform_get_drvdata(pdev);
>> +
>> +	iounmap(priv->avs_intr_base);
>> +	iounmap(priv->base);
>> +}
>> +
>>   static int brcm_avs_cpufreq_init(struct cpufreq_policy *policy)
>>   {
>>   	struct cpufreq_frequency_table *freq_table;
>> @@ -732,21 +742,26 @@ static int brcm_avs_cpufreq_probe(struct platform_device *pdev)
>>   
>>   	brcm_avs_driver.driver_data = pdev;
>>   
>> -	return cpufreq_register_driver(&brcm_avs_driver);
>> +	ret = cpufreq_register_driver(&brcm_avs_driver);
>> +	if (ret)
>> +		goto err_uninit;
>> +
>> +	return 0;
>> +
>> +err_uninit:
>> +	brcm_avs_prepare_uninit(pdev);
>> +	return ret;
> 
> Maybe rewrite as:
> 
> 	ret = cpufreq_register_driver(&brcm_avs_driver);
> 	if (ret)
>                  brcm_avs_prepare_uninit(pdev);
> 	return ret;
> 

Personlaly, I prefer what I have proposed. Having a clear and dedicated 
error handling path is more future proff, IMHO.

>>   }
>>   
>>   static int brcm_avs_cpufreq_remove(struct platform_device *pdev)
>>   {
>> -	struct private_data *priv;
>>   	int ret;
>>   
>>   	ret = cpufreq_unregister_driver(&brcm_avs_driver);
>>   	if (ret)
>>   		return ret;
> 
> Instead of returning here, it can be just WARN_ON(ret); and then go on and free
> the resources and this needs to be done in a separate patch.

Ok, I agree (see my comment below the --- in my patch).
I'll send a patch for it when the first patch will be applied, unless 
you prefer if I resend as a serie.

CJ

> 
>>   
>> -	priv = platform_get_drvdata(pdev);
>> -	iounmap(priv->base);
>> -	iounmap(priv->avs_intr_base);
>> +	brcm_avs_prepare_uninit(pdev);
>>   
>>   	return 0;
>>   }
>