device property: Fix reading pset strings using array access functions

The length field value of non-array string properties is the length of the
string itself. Non-array string properties thus require specific handling.
Fix this.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/property.c

@@ -147,14 +147,36 @@ static int pset_prop_read_string_array(struct property_set *pset,
 				       const char *propname,
 				       const char **strings, size_t nval)
 {
+	const struct property_entry *prop;
 	const void *pointer;
-	size_t length = nval * sizeof(*strings);
+	size_t array_len, length;
+
+	/* Find out the array length. */
+	prop = pset_prop_get(pset, propname);
+	if (!prop)
+		return -EINVAL;
+
+	if (!prop->is_array)
+		/* The array length for a non-array string property is 1. */
+		array_len = 1;
+	else
+		/* Find the length of an array. */
+		array_len = pset_prop_count_elems_of_size(pset, propname,
+							  sizeof(const char *));
+
+	/* Return how many there are if strings is NULL. */
+	if (!strings)
+		return array_len;
+
+	array_len = min(nval, array_len);
+	length = array_len * sizeof(*strings);
 
 	pointer = pset_prop_find(pset, propname, length);
 	if (IS_ERR(pointer))
 		return PTR_ERR(pointer);
 
 	memcpy(strings, pointer, length);
+
 	return 0;
 }
 
@@ -555,12 +577,8 @@ static int __fwnode_property_read_string_array(struct fwnode_handle *fwnode,
 		return acpi_node_prop_read(fwnode, propname, DEV_PROP_STRING,
 					   val, nval);
 	else if (is_pset_node(fwnode))
-		return val ?
-			pset_prop_read_string_array(to_pset_node(fwnode),
-						    propname, val, nval) :
-			pset_prop_count_elems_of_size(to_pset_node(fwnode),
-						      propname,
-						      sizeof(const char *));
+		return pset_prop_read_string_array(to_pset_node(fwnode),
+						   propname, val, nval);
 	return -ENXIO;
 }