thermal: Fix potential NULL pointer accesses

The type parameter in thermal_zone_device_register and
thermal_cooling_device_register can be NULL, indicating that no sysfs attribute
for the type should be created. Only call strlen() and strcpy() on type if it is
not NULL.

This patch addresses Coverity #102180 and #102182: Dereference before null check
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NZhang Rui <rui.zhang@intel.com>

drivers/thermal/thermal_sys.c

@@ -901,7 +901,7 @@ thermal_cooling_device_register(char *type, void *devdata,
 	struct thermal_zone_device *pos;
 	int result;
 
-	if (strlen(type) >= THERMAL_NAME_LENGTH)
+	if (type && strlen(type) >= THERMAL_NAME_LENGTH)
 		return ERR_PTR(-EINVAL);
 
 	if (!ops || !ops->get_max_state || !ops->get_cur_state ||
@@ -918,7 +918,7 @@ thermal_cooling_device_register(char *type, void *devdata,
 		return ERR_PTR(result);
 	}
 
-	strcpy(cdev->type, type);
+	strcpy(cdev->type, type ? : "");
 	mutex_init(&cdev->lock);
 	INIT_LIST_HEAD(&cdev->thermal_instances);
 	cdev->ops = ops;
@@ -1344,7 +1344,7 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
 	int count;
 	int passive = 0;
 
-	if (strlen(type) >= THERMAL_NAME_LENGTH)
+	if (type && strlen(type) >= THERMAL_NAME_LENGTH)
 		return ERR_PTR(-EINVAL);
 
 	if (trips > THERMAL_MAX_TRIPS || trips < 0 || mask >> trips)
@@ -1366,7 +1366,7 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
 		return ERR_PTR(result);
 	}
 
-	strcpy(tz->type, type);
+	strcpy(tz->type, type ? : "");
 	tz->ops = ops;
 	tz->device.class = &thermal_class;
 	tz->devdata = devdata;