ACPI / property: fix handling of data_nodes in acpi_get_next_subnode()

When the DSDT tables expose devices with subdevices and a set of
hierarchical _DSD properties, the data returned by
acpi_get_next_subnode() is incorrect, with the results suggesting a bad
pointer assignment. The parser works fine with device_nodes or
data_nodes, but not with a combination of the two.

The problem is traced to an invalid pointer used when jumping from
handling device_nodes to data nodes. The existing code looks for data
nodes below the last subdevice found instead of the common root. Fix
by forcing the acpi_device pointer to be derived from the same fwnode
for the two types of subnodes.

This same problem of handling device and data nodes was already fixed
in a similar way by 'commit bf4703fd ("ACPI / property: fix data
node parsing in acpi_get_next_subnode()")' but broken later by 'commit
34055190 ("ACPI / property: Add fwnode_get_next_child_node()")', so
this should probably go to linux-stable all the way to 4.12
Signed-off-by: NPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/property.c

@@ -1032,6 +1032,14 @@ struct fwnode_handle *acpi_get_next_subnode(const struct fwnode_handle *fwnode,
 		const struct acpi_data_node *data = to_acpi_data_node(fwnode);
 		struct acpi_data_node *dn;
 
+		/*
+		 * We can have a combination of device and data nodes, e.g. with
+		 * hierarchical _DSD properties. Make sure the adev pointer is
+		 * restored before going through data nodes, otherwise we will
+		 * be looking for data_nodes below the last device found instead
+		 * of the common fwnode shared by device_nodes and data_nodes.
+		 */
+		adev = to_acpi_device_node(fwnode);
 		if (adev)
 			head = &adev->data.subnodes;
 		else if (data)