driver core: bus: Return -EIO instead of 0 when show/store invalid bus attribute

Return -EIO instead of 0 for below erroneous bus attribute operations:
 - read a bus attribute without show().
 - write a bus attribute without store().

Signed-off-by: Zijun Hu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: zijun-hu

drivers/base/bus.c

@@ -152,7 +152,8 @@ static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
 {
 	struct bus_attribute *bus_attr = to_bus_attr(attr);
 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
-	ssize_t ret = 0;
+	/* return -EIO for reading a bus attribute without show() */
+	ssize_t ret = -EIO;
 
 	if (bus_attr->show)
 		ret = bus_attr->show(subsys_priv->bus, buf);
@@ -164,7 +165,8 @@ static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
 {
 	struct bus_attribute *bus_attr = to_bus_attr(attr);
 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
-	ssize_t ret = 0;
+	/* return -EIO for writing a bus attribute without store() */
+	ssize_t ret = -EIO;
 
 	if (bus_attr->store)
 		ret = bus_attr->store(subsys_priv->bus, buf, count);