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[PATCH 1/4] PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()

Lifeng Zheng posted 4 patches 7 months, 3 weeks ago
[PATCH 1/4] PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()
Posted by Lifeng Zheng 7 months, 3 weeks ago 
Replace sscanf() with kstrtoul() in set_freq_store() and check the result
to avoid invalid input.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
---
 drivers/devfreq/governor_userspace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
index d1aa6806b683..175de0c0b50e 100644
--- a/drivers/devfreq/governor_userspace.c
+++ b/drivers/devfreq/governor_userspace.c
@@ -9,6 +9,7 @@
 #include <linux/slab.h>
 #include <linux/device.h>
 #include <linux/devfreq.h>
+#include <linux/kstrtox.h>
 #include <linux/pm.h>
 #include <linux/mutex.h>
 #include <linux/module.h>
@@ -39,10 +40,13 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
 	unsigned long wanted;
 	int err = 0;
 
+	err = kstrtoul(buf, 0, &wanted);
+	if (err)
+		return err;
+
 	mutex_lock(&devfreq->lock);
 	data = devfreq->governor_data;
 
-	sscanf(buf, "%lu", &wanted);
 	data->user_frequency = wanted;
 	data->valid = true;
 	err = update_devfreq(devfreq);
-- 
2.33.0
Re: [PATCH 1/4] PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()
Posted by Chanwoo Choi 7 months ago 
Hi,

Applied it. Thanks.

On Mon, Apr 21, 2025 at 12:00 PM Lifeng Zheng <zhenglifeng1@huawei.com> wrote:
>
> Replace sscanf() with kstrtoul() in set_freq_store() and check the result
> to avoid invalid input.
>
> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
> ---
>  drivers/devfreq/governor_userspace.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
> index d1aa6806b683..175de0c0b50e 100644
> --- a/drivers/devfreq/governor_userspace.c
> +++ b/drivers/devfreq/governor_userspace.c
> @@ -9,6 +9,7 @@
>  #include <linux/slab.h>
>  #include <linux/device.h>
>  #include <linux/devfreq.h>
> +#include <linux/kstrtox.h>
>  #include <linux/pm.h>
>  #include <linux/mutex.h>
>  #include <linux/module.h>
> @@ -39,10 +40,13 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
>         unsigned long wanted;
>         int err = 0;
>
> +       err = kstrtoul(buf, 0, &wanted);
> +       if (err)
> +               return err;
> +
>         mutex_lock(&devfreq->lock);
>         data = devfreq->governor_data;
>
> -       sscanf(buf, "%lu", &wanted);
>         data->user_frequency = wanted;
>         data->valid = true;
>         err = update_devfreq(devfreq);
> --
> 2.33.0
>
>


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics
Re: [PATCH 1/4] PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()
Posted by David Laight 7 months, 3 weeks ago 
On Mon, 21 Apr 2025 11:00:17 +0800
Lifeng Zheng <zhenglifeng1@huawei.com> wrote:

> Replace sscanf() with kstrtoul() in set_freq_store() and check the result
> to avoid invalid input.

Isn't this a UAPI change?

The sscanf() version will ignore trailing characters.
In this case it is actually likely that value might have a trailing "Hz".

	David

> 
> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
> ---
>  drivers/devfreq/governor_userspace.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
> index d1aa6806b683..175de0c0b50e 100644
> --- a/drivers/devfreq/governor_userspace.c
> +++ b/drivers/devfreq/governor_userspace.c
> @@ -9,6 +9,7 @@
>  #include <linux/slab.h>
>  #include <linux/device.h>
>  #include <linux/devfreq.h>
> +#include <linux/kstrtox.h>
>  #include <linux/pm.h>
>  #include <linux/mutex.h>
>  #include <linux/module.h>
> @@ -39,10 +40,13 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
>  	unsigned long wanted;
>  	int err = 0;
>  
> +	err = kstrtoul(buf, 0, &wanted);
> +	if (err)
> +		return err;
> +
>  	mutex_lock(&devfreq->lock);
>  	data = devfreq->governor_data;
>  
> -	sscanf(buf, "%lu", &wanted);
>  	data->user_frequency = wanted;
>  	data->valid = true;
>  	err = update_devfreq(devfreq);
Re: [PATCH 1/4] PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()
Posted by zhenglifeng (A) 7 months, 2 weeks ago 
On 2025/4/27 19:17, David Laight wrote:
> On Mon, 21 Apr 2025 11:00:17 +0800
> Lifeng Zheng <zhenglifeng1@huawei.com> wrote:
> 
>> Replace sscanf() with kstrtoul() in set_freq_store() and check the result
>> to avoid invalid input.
> 
> Isn't this a UAPI change?
> 
> The sscanf() version will ignore trailing characters.
> In this case it is actually likely that value might have a trailing "Hz".

I tried to still use sscanf() at first, but checkpatch warned: "Prefer
kstrto<type> to single variable sscanf".

I'm not sure if we should ignore this warning.

> 
> 	David
> 
>>
>> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
>> ---
>>  drivers/devfreq/governor_userspace.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
>> index d1aa6806b683..175de0c0b50e 100644
>> --- a/drivers/devfreq/governor_userspace.c
>> +++ b/drivers/devfreq/governor_userspace.c
>> @@ -9,6 +9,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/device.h>
>>  #include <linux/devfreq.h>
>> +#include <linux/kstrtox.h>
>>  #include <linux/pm.h>
>>  #include <linux/mutex.h>
>>  #include <linux/module.h>
>> @@ -39,10 +40,13 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
>>  	unsigned long wanted;
>>  	int err = 0;
>>  
>> +	err = kstrtoul(buf, 0, &wanted);
>> +	if (err)
>> +		return err;
>> +
>>  	mutex_lock(&devfreq->lock);
>>  	data = devfreq->governor_data;
>>  
>> -	sscanf(buf, "%lu", &wanted);
>>  	data->user_frequency = wanted;
>>  	data->valid = true;
>>  	err = update_devfreq(devfreq);
> 
>

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