linux-kernel - Re: [PATCH] usb: musb: Fix runtime PM imbalance on error

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Message-ID: <20200521203728.GB25575@iaqt7>
Date:   Thu, 21 May 2020 15:37:28 -0500
From:   Bin Liu <b-liu@...com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
CC:     <kjlu@....edu>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: musb: Fix runtime PM imbalance on error

Hi,

On Thu, May 21, 2020 at 03:35:47PM +0800, Dinghao Liu wrote:
> When copy_from_user() returns an error code, a pairing
> runtime PM usage counter decrement is needed to keep
> the counter balanced.
> 
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/usb/musb/musb_debugfs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/musb/musb_debugfs.c b/drivers/usb/musb/musb_debugfs.c
> index 7b6281ab62ed..837c38a5e4ef 100644
> --- a/drivers/usb/musb/musb_debugfs.c
> +++ b/drivers/usb/musb/musb_debugfs.c
> @@ -178,8 +178,11 @@ static ssize_t musb_test_mode_write(struct file *file,
>  
>  	memset(buf, 0x00, sizeof(buf));
>  
> -	if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
> +	if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count))) {
> +		pm_runtime_mark_last_busy(musb->controller);
> +		pm_runtime_put_autosuspend(musb->controller);
>  		return -EFAULT;
> +	}

Thanks for catching the bug. Can you please instead move these lines to
the beginning of this function so that pm_runtime_get_sync() is not
called if copy_from_user() failed?

-Bin.