[v2] cpufreq: warn about invalid vals to scaling_max/min_freq interfaces

When echo an invalid val to scaling_min_freq:
> echo 123abc123 > scaling_min_freq
It looks weird to have a return val of 0:
> echo $?
> 0

Sane people won't echo strings like that into these interfaces but fuzz
tests may do. Also, maybe it's better to inform people if input is
invalid.

After this:
> echo 123abc123 > scaling_min_freq
> -bash: echo: write error: Invalid argument

Signed-off-by: qinyu <qinyu32@huawei.com>
Tested-by: zhangxiaofeng <zhangxiaofeng46@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
v2:
- reword commit message to match the actual code changes.
 drivers/cpufreq/cpufreq.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

On Mon, Mar 20, 2023 at 9:09 AM qinyu <qinyu32@huawei.com> wrote:
>
> When echo an invalid val to scaling_min_freq:
> > echo 123abc123 > scaling_min_freq
> It looks weird to have a return val of 0:
> > echo $?
> > 0
>
> Sane people won't echo strings like that into these interfaces but fuzz
> tests may do. Also, maybe it's better to inform people if input is
> invalid.
>
> After this:
> > echo 123abc123 > scaling_min_freq
> > -bash: echo: write error: Invalid argument
>
> Signed-off-by: qinyu <qinyu32@huawei.com>
> Tested-by: zhangxiaofeng <zhangxiaofeng46@huawei.com>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> v2:
> - reword commit message to match the actual code changes.
>  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 6d8fd3b8d..d61f7308f 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -725,9 +725,9 @@ static ssize_t store_##file_name                                    \
>         unsigned long val;                                              \
>         int ret;                                                        \
>                                                                         \
> -       ret = sscanf(buf, "%lu", &val);                                 \
> -       if (ret != 1)                                                   \
> -               return -EINVAL;                                         \
> +       ret = kstrtoul(buf, 0, &val);                                   \
> +       if (ret)                                                        \
> +               return ret;                                             \
>                                                                         \
>         ret = freq_qos_update_request(policy->object##_freq_req, val);\
>         return ret >= 0 ? count : ret;                                  \
> --

Applied as 6.4 material, thanks!