linux-kernel - Re: [PATCH 2/3] dmaengine: usb-dmac: Fix PM reference leak in usb_dmac

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Date:   Mon, 31 May 2021 14:11:22 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Vinod Koul <vkoul@...nel.org>
CC:     <mcoquelin.stm32@...il.com>, <alexandre.torgue@...s.st.com>,
        <michal.simek@...inx.com>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <yi.zhang@...wei.com>
Subject: Re: [PATCH 2/3] dmaengine: usb-dmac: Fix PM reference leak in
 usb_dmac_probe()

On 2021/05/31 12:00, Vinod Koul wrote:
> On 17-05-21, 16:18, Yu Kuai wrote:
>> pm_runtime_get_sync will increment pm usage counter even it failed.
>> Forgetting to putting operation will result in reference leak here.
>> Fix it by replacing it with pm_runtime_resume_and_get to keep usage
>> counter balanced.
>>
>> Reported-by: Hulk Robot <hulkci@...wei.com>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   drivers/dma/sh/usb-dmac.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/sh/usb-dmac.c b/drivers/dma/sh/usb-dmac.c
>> index 8f7ceb698226..2a6c8fd8854e 100644
>> --- a/drivers/dma/sh/usb-dmac.c
>> +++ b/drivers/dma/sh/usb-dmac.c
>> @@ -796,7 +796,7 @@ static int usb_dmac_probe(struct platform_device *pdev)
>>   
>>   	/* Enable runtime PM and initialize the device. */
>>   	pm_runtime_enable(&pdev->dev);
>> -	ret = pm_runtime_get_sync(&pdev->dev);
>> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> 
> This does not seem to fix anything.. the below goto goes and disables
> the runtime_pm for this device and thus there wont be any leak
Hi,

If pm_runtime_get_sync() fails and increments the pm.usage_count
variable, pm_runtime_disable() does not reset the counter, and
we still need to decrement the usage count when pm_runtime_get_sync()
fails. Do I miss anthing?

Thansk!
Yu Kuai
> 
>>   	if (ret < 0) {
>>   		dev_err(&pdev->dev, "runtime PM get sync failed (%d)\n", ret);
>>   		goto error_pm;
>> -- 
>> 2.25.4
>