PM / devfreq: governor: Replace sscanf() with kstrtoul() in set_freq_store()

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

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Link: https://lore.kernel.org/lkml/20250421030020.3108405-2-zhenglifeng1@huawei.com/
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

Author: Lifeng Zheng

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);