linux-kernel - Re: [PATCH v2] hwrng: exynos - fix reference leak in exynos_trng

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Date:   Wed, 02 Dec 2020 11:14:10 +0100
From:   Lukasz Stelmach <l.stelmach@...sung.com>
To:     Qinglang Miao <miaoqinglang@...wei.com>
Cc:     "Krzysztof Kozlowski" <krzk@...nel.org>,
        <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 v2] hwrng: exynos - fix reference leak in
 exynos_trng_probe

It was <2020-11-30 pon 21:01>, when Qinglang Miao wrote:
> pm_runtime_get_sync will increment pm usage counter even
> failed. Forgetting to putting operation will result in a
> reference leak here.
>
> Replace it with pm_runtime_resume_and_get to keep usage
> counter balanced. I remove err_clock label at the same.
>
> Fixes: 6cd225cc5d8a ("hwrng: exynos - add Samsung Exynos True RNG driver")
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Suggested-by: Lukasz Stelmach <l.stelmach@...sung.com>
> Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com>
> ---
>  v2: remobe useless label as Lukasz suggested.

That is good too, but I meant using pm_runtime_resume_and_get() in
exynos_trng_resume() too. Please take a look at that function.

>
>  drivers/char/hw_random/exynos-trng.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/char/hw_random/exynos-trng.c b/drivers/char/hw_random/exynos-trng.c
> index 8e1fe3f8d..ffebb72e4 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;
> @@ -142,13 +142,13 @@ static int exynos_trng_probe(struct platform_device *pdev)
>  	if (IS_ERR(trng->clk)) {
>  		ret = PTR_ERR(trng->clk);
>  		dev_err(&pdev->dev, "Could not get clock.\n");
> -		goto err_clock;
> +		goto err_pm_get;
>  	}
>  
>  	ret = clk_prepare_enable(trng->clk);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Could not enable the clk.\n");
> -		goto err_clock;
> +		goto err_pm_get;
>  	}
>  
>  	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
> @@ -164,9 +164,6 @@ static int exynos_trng_probe(struct platform_device *pdev)
>  err_register:
>  	clk_disable_unprepare(trng->clk);
>  
> -err_clock:
> -	pm_runtime_put_sync(&pdev->dev);
> -
>  err_pm_get:
>  	pm_runtime_disable(&pdev->dev);

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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