linux-kernel - Re: [PATCH] cpufreq: Update sscanf() to kstrtouint()

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Message-ID: <20250519224648.41f2460d@pumpkin>
Date: Mon, 19 May 2025 22:46:48 +0100
From: David Laight <david.laight.linux@...il.com>
To: Bowen Yu <yubowen8@...wei.com>
Cc: <rafael@...nel.org>, <viresh.kumar@...aro.org>,
 <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linuxarm@...wei.com>, <zhanjie9@...ilicon.com>,
 <jonathan.cameron@...wei.com>, <lihuisong@...wei.com>,
 <zhenglifeng1@...wei.com>, <cenxinghai@...artners.com>
Subject: Re: [PATCH] cpufreq: Update sscanf() to kstrtouint()

On Mon, 19 May 2025 15:09:38 +0800
Bowen Yu <yubowen8@...wei.com> wrote:

> In store_scaling_setspeed(), sscanf is still used to read to sysfs.
> Newer kstrtox provide more features including overflow protection,
> better errorhandling and allows for other systems of numeration. It
> is therefore better to update sscanf() to kstrtouint().

This is a UAPI change.
Since the value is a frequency there could easily be scripts
that append Hz to the value.
You're making them fail.

	David

> 
> Signed-off-by: Bowen Yu <yubowen8@...wei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index be727da0be4d..0c842edd1a76 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -920,9 +920,9 @@ static ssize_t store_scaling_setspeed(struct cpufreq_policy *policy,
>  	if (!policy->governor || !policy->governor->store_setspeed)
>  		return -EINVAL;
>  
> -	ret = sscanf(buf, "%u", &freq);
> -	if (ret != 1)
> -		return -EINVAL;
> +	ret = kstrtouint(buf, 0, &freq);
> +	if (ret)
> +		return ret;
>  
>  	policy->governor->store_setspeed(policy, freq);
>