linux-kernel - Re: [PATCH] hwrng: exynos - fix reference leak in exynos_trng

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Date:   Mon, 30 Nov 2020 21:03:41 +0800
From:   Qinglang Miao <miaoqinglang@...wei.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
CC:     Łukasz Stelmach <l.stelmach@...sung.com>,
        <linux-samsung-soc@...r.kernel.org>,
        <linux-crypto@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hwrng: exynos - fix reference leak in exynos_trng_probe



在 2020/11/27 17:44, Krzysztof Kozlowski 写道:
> On Fri, Nov 27, 2020 at 05:44:46PM +0800, Qinglang Miao wrote:
>> pm_runtime_get_sync will increment pm usage counter even it
>> failed. Forgetting to putting operation will result in a
>> reference leak here.
>>
>> A new function pm_runtime_resume_and_get is introduced in
>> [0] to keep usage counter balanced. So We fix the reference
>> leak by replacing it with new funtion.
>>
>> [0] dd8088d5a896 ("PM: runtime: Add  pm_runtime_resume_and_get to deal with usage counter")
> 
> Do not put such dependencies into the commit message - it does not bring
> useful information to the history. Store it under '---' separator.
> 
>>
>> Fixes: 6cd225cc5d8a ("hwrng: exynos - add Samsung Exynos True RNG driver")
>> Reported-by: Hulk Robot <hulkci@...wei.com>
>> Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com>
>> ---
>>   drivers/char/hw_random/exynos-trng.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/hw_random/exynos-trng.c b/drivers/char/hw_random/exynos-trng.c
>> index 8e1fe3f8d..666246bc8 100644
>> --- a/drivers/char/hw_random/exynos-trng.c
>> +++ b/drivers/char/hw_random/exynos-trng.c
>> @@ -132,7 +132,7 @@ static int exynos_trng_probe(struct platform_device *pdev)
>>   		return PTR_ERR(trng->mem);
>>   
>>   	pm_runtime_enable(&pdev->dev);
>> -	ret = pm_runtime_get_sync(&pdev->dev);
>> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> 
> This cannot be applied. Fix it by replacing err_clock label with this
> one. >
> Best regards,
> Krzysztof
> 
> .
Hi Krzysztof,

I realize that there's a mistake in this patch through your reply.

There's two way to fix this one:
1) replace err_pm_get with err_clock label when pm_runtime_get_sync fails.
2) replace pm_runtime_get_sync with pm_runtime_resume_and_get and remove
redundant label(err_clock).

I take 2) on v2 for it makes codes more clearer in a way.

Thanks.

>