[PATCH v3 0/2] device property: fix child iteration issues with secondary fwnodes

[Xu Yang]

This series fixes two issues in the fwnode child iteration logic when
a secondary fwnode is present.

The first issue is  a refcount imbalance in software_node_get_next_child().
When a software node is used as a secondary fwnode, the iteration code may
incorrectly decrement the refcount of child nodes that do not belong to the
software node hierarchy. This results in refcount underflow and possible
use-after-free.

The second issue is an infinite loop in fwnode_for_each_child_node(), caused
by improper handling of iteration state across primary and secondary fwnodes.
When iterating over children from both primary and secondary fwnodes, the code
may incorrectly resume iteration from the primary fwnode even when the current
child belongs to the secondary, leading to repeated traversal and a loop.

Both issues are triggered when mixing different fwnode types through the
secondary mechanism, and stem from incorrect assumptions about ownership
and traversal context of child nodes.

---
Changes in v3:
- remove software node patch 
- add a kunit test case suggested by Andy Shevchenko
- Link to v2: https://patch.msgid.link/20260603-fixes_fwnode_iteration-v2-0-0ae381f8b7b9@xxxxxxx

Changes in v2:
- use __free() to cleanup parent fwnode
- Link to v1: https://lore.kernel.org/r/20260525-fixes_fwnode_iteration-v1-0-a12903fb2919@xxxxxxx

To: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
To: Daniel Scally <djrscally@xxxxxxxxx>
To: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
To: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
To: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
To: Danilo Krummrich <dakr@xxxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx
Cc: driver-core@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

---
Xu Yang (2):
      device property: fix infinite loop in fwnode_for_each_child_node()
      drivers: base: test: add test cases for fwnode_for_each_child_node()

 drivers/base/property.c                 |  18 ++++-
 drivers/base/test/Kconfig               |   1 +
 drivers/base/test/property-entry-test.c | 136 ++++++++++++++++++++++++++++++++
 3 files changed, 152 insertions(+), 3 deletions(-)
---
base-commit: b7bee4ca5688e30ca50fbc87b1b8f7eed7006c17
change-id: 20260525-fixes_fwnode_iteration-baf62d861305

Best regards,
--  
Xu Yang <xu.yang_2@xxxxxxx>