linux-kernel - RE: [PATCH v1 2/9] pktcdvd: replace sscanf() by kstrtoul()

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Message-ID: <4f4c89f2c0924f05a894a1457c63ee4c@AcuMS.aculab.com>
Date:   Thu, 19 Jan 2023 22:40:12 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>,
        Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v1 2/9] pktcdvd: replace sscanf() by kstrtoul()

From: Andy Shevchenko
> Sent: 19 January 2023 22:08
> 
> The checkpatch.pl warns: "Prefer kstrto<type> to single variable sscanf".
> Fix the code accordingly.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/block/pktcdvd.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
> index 0ec8dc8ee5ed..ad4336ae9927 100644
> --- a/drivers/block/pktcdvd.c
> +++ b/drivers/block/pktcdvd.c
> @@ -236,15 +236,16 @@ static ssize_t congestion_off_store(struct device *dev,
>  				    const char *buf, size_t len)
>  {
>  	struct pktcdvd_device *pd = dev_get_drvdata(dev);
> -	int val;
> +	int val, ret;
> 
> -	if (sscanf(buf, "%d", &val) == 1) {
> -		spin_lock(&pd->lock);
> -		pd->write_congestion_off = val;
> -		init_write_congestion_marks(&pd->write_congestion_off,
> -					&pd->write_congestion_on);
> -		spin_unlock(&pd->lock);
> -	}
> +	ret = kstrtoint(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	spin_lock(&pd->lock);
> +	pd->write_congestion_off = val;
> +	init_write_congestion_marks(&pd->write_congestion_off, &pd->write_congestion_on);
> +	spin_unlock(&pd->lock);
>  	return len;
>  }

These don't look directly equivalent.
The sscanf() version silently ignores trailing characters.
I think kstrtoint() will generate an error.
Have you actually checked that the caller allows for
an error return.

	David

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