thermal: fix potential out-of-bounds memory access

temp_crit.name and temp_input.name have a length of 16 bytes.  Using
THERMAL_NAME_LENGTH (20) as length parameter for snprintf() may result in
out-of-bounds memory accesses.  Replace it with sizeof().

Addresses Coverity #115679

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Len Brown <lenb@kernel.org>
Cc: "Brown, Len" <len.brown@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/thermal_sys.c

@@ -598,7 +598,7 @@ thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 	temp->tz = tz;
 	hwmon->count++;
 
-	snprintf(temp->temp_input.name, THERMAL_NAME_LENGTH,
+	snprintf(temp->temp_input.name, sizeof(temp->temp_input.name),
 		 "temp%d_input", hwmon->count);
 	temp->temp_input.attr.attr.name = temp->temp_input.name;
 	temp->temp_input.attr.attr.mode = 0444;
@@ -611,7 +611,8 @@ thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 	if (tz->ops->get_crit_temp) {
 		unsigned long temperature;
 		if (!tz->ops->get_crit_temp(tz, &temperature)) {
-			snprintf(temp->temp_crit.name, THERMAL_NAME_LENGTH,
+			snprintf(temp->temp_crit.name,
+				 sizeof(temp->temp_crit.name),
 				"temp%d_crit", hwmon->count);
 			temp->temp_crit.attr.attr.name = temp->temp_crit.name;
 			temp->temp_crit.attr.attr.mode = 0444;