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Subject: Re: [PATCH] hwrng: exynos - fix reference leak in exynos_trng_probe
To:     Lukasz Stelmach <l.stelmach@samsung.com>
CC:     Krzysztof Kozlowski <krzk@kernel.org>,
        <linux-samsung-soc@vger.kernel.org>,
        <linux-crypto@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <20201127094446.121277-1-miaoqinglang@huawei.com>
 <CGME20201127142637eucas1p1746be156c43e789b48b5b78b9b212a33@eucas1p1.samsung.com>
 <dleftjlfemg9kh.fsf%l.stelmach@samsung.com>
From:   Qinglang Miao <miaoqinglang@huawei.com>
Message-ID: <3ed654dd-db10-0975-d125-a3949c9bab90@huawei.com>
Date:   Mon, 30 Nov 2020 21:05:55 +0800
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在 2020/11/27 22:26, Lukasz Stelmach 写道:
> It was <2020-11-27 pią 17:44>, when 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")
>>
>> Fixes: 6cd225cc5d8a ("hwrng: exynos - add Samsung Exynos True RNG driver")
>> Reported-by: Hulk Robot <hulkci@huawei.com>
>> Signed-off-by: Qinglang Miao <miaoqinglang@huawei.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);
>>   	if (ret < 0) {
>>   		dev_err(&pdev->dev, "Could not get runtime PM.\n");
>>   		goto err_pm_get;
> 
> Thanks. I suppose you may use the new function exynos_trng_resume(),
> remove everything and leave only
> 
> return pm_runtime_resume_and_get(dev);
Hi, Lukasz

I sent a v2 on this one.

But I'm not really sure about what does 'remove everything' mean. for 
example, should I remove exynos_trng_resume in this patch?

Thanks.
>