cpufreq: conservative: Replace sscanf() with kstrtouint()

Replace sscanf() with kstrtouint() in all sysfs store functions to improve
input validation and security. The kstrtouint() function provides better
error detection, overflow protection, and consistent error handling
compared to sscanf().

This maintains existing functionality while improving input validation
robustness and following kernel coding best practices for string parsing.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20250906115316.3010384-1-kaushlendra.kumar@intel.com
[ rjw: Dropped duplicate paragraph from the changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: kaushlen

drivers/cpufreq/cpufreq_conservative.c

@@ -152,9 +152,9 @@ static ssize_t sampling_down_factor_store(struct gov_attr_set *attr_set,
 	struct dbs_data *dbs_data = to_dbs_data(attr_set);
 	unsigned int input;
 	int ret;
-	ret = sscanf(buf, "%u", &input);
+	ret = kstrtouint(buf, 0, &input);
 
-	if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
+	if (ret || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 		return -EINVAL;
 
 	dbs_data->sampling_down_factor = input;
@@ -168,9 +168,9 @@ static ssize_t up_threshold_store(struct gov_attr_set *attr_set,
 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 	unsigned int input;
 	int ret;
-	ret = sscanf(buf, "%u", &input);
+	ret = kstrtouint(buf, 0, &input);
 
-	if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
+	if (ret || input > 100 || input <= cs_tuners->down_threshold)
 		return -EINVAL;
 
 	dbs_data->up_threshold = input;
@@ -184,10 +184,10 @@ static ssize_t down_threshold_store(struct gov_attr_set *attr_set,
 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 	unsigned int input;
 	int ret;
-	ret = sscanf(buf, "%u", &input);
+	ret = kstrtouint(buf, 0, &input);
 
 	/* cannot be lower than 1 otherwise freq will not fall */
-	if (ret != 1 || input < 1 || input >= dbs_data->up_threshold)
+	if (ret || input < 1 || input >= dbs_data->up_threshold)
 		return -EINVAL;
 
 	cs_tuners->down_threshold = input;
@@ -201,9 +201,9 @@ static ssize_t ignore_nice_load_store(struct gov_attr_set *attr_set,
 	unsigned int input;
 	int ret;
 
-	ret = sscanf(buf, "%u", &input);
-	if (ret != 1)
-		return -EINVAL;
+	ret = kstrtouint(buf, 0, &input);
+	if (ret)
+		return ret;
 
 	if (input > 1)
 		input = 1;
@@ -226,10 +226,10 @@ static ssize_t freq_step_store(struct gov_attr_set *attr_set, const char *buf,
 	struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
 	unsigned int input;
 	int ret;
-	ret = sscanf(buf, "%u", &input);
+	ret = kstrtouint(buf, 0, &input);
 
-	if (ret != 1)
-		return -EINVAL;
+	if (ret)
+		return ret;
 
 	if (input > 100)
 		input = 100;