Re: [PATCH] devfreq: replace sscanf with kstrtol
From: Chanwoo Choi
Date: Fri Aug 04 2017 - 11:13:44 EST
Hi,
On Fri, Aug 4, 2017 at 12:57 PM, <gsantosh@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> Adding error checks to devfreq userspace governor, the current
> implementation results in setting wrong
> frequency when sscanf returns error.
>
>
> From 12e0a347addd70529b2c378299b27b65f0766f99 Mon Sep 17 00:00:00 2001
> From: Santosh Mardi <gsantosh@xxxxxxxxxxxxxx>
> Date: Tue, 25 Jul 2017 18:47:11 +0530
> Subject: [PATCH] devfreq: replace sscanf with kstrtol
>
> store_freq function of devfreq userspace governor
> executes further, even if error is returned from sscanf,
> this will result in setting up wrong frequency value.
>
> The usage for the sscanf is only for single variable so
> replace sscanf with kstrtol along with error check to
> bail out if any error is returned.
>
> Signed-off-by: Santosh Mardi <gsantosh@xxxxxxxxxxxxxx>
> ---
> drivers/devfreq/governor_userspace.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/devfreq/governor_userspace.c
> b/drivers/devfreq/governor_userspace.c
> index 77028c2..a84796d 100644
> --- a/drivers/devfreq/governor_userspace.c
> +++ b/drivers/devfreq/governor_userspace.c
> @@ -53,12 +53,15 @@ static ssize_t store_freq(struct device *dev, struct
> device_attribute *attr,
> mutex_lock(&devfreq->lock);
> data = devfreq->data;
>
> - sscanf(buf, "%lu", &wanted);
> + err = kstrtol(buf, 0, &wanted);
> + if (err < 0)
> + goto out;
I think that just you can check the return value as following:
The other point of devfreq already uses the following style
to check the return value of sscanf. I think kstrtol is not necessary.
err = sscanf(buf, "%lu", &wanted);
if (err != 1)
goto out;
And please use the scripts/get_maintainer.pl
in order to prevent the missing of the reviewer.
> data->user_frequency = wanted;
> data->valid = true;
> err = update_devfreq(devfreq);
> if (err == 0)
> err = count;
> +out:
> mutex_unlock(&devfreq->lock);
> return err;
> }
> --
>
> Regards,
> Santosh M G.
> Qualcomm Innovation Center
--
Best Regards,
Chanwoo Choi
Samsung Electronics