[PATCH master 1/4] of: only replace a device tree that is actually tentative

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

barebox_register_of() is called a second time when the EFI payload
registers a device tree read from the EFI system partition on top of the
tentative empty device tree registered earlier at core_initcall.

The check that is meant to allow this looks at the children of the newly
passed device tree instead of those of the already registered one, so it
rejects exactly the case it was added for: registering a populated
device tree over the empty placeholder returns -EBUSY, while an empty
device tree may silently replace a fully populated one.

Look at the registered root node instead.

Fixes: 10922345fbcc ("efi: payload: register dummy device tree")
Assisted-by: Claude:opus-5
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/of/base.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 62d452907a57..2a2edc167cc6 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2151,7 +2151,11 @@ of_populate_initcall(barebox_of_populate);
 int barebox_register_of(struct device_node *root)
 {
 	if (root_node) {
-		if (!list_empty(&root->children))
+		/*
+		 * Only a tentative device tree, i.e. one without any nodes,
+		 * may be replaced by a real one.
+		 */
+		if (!list_empty(&root_node->children))
 			return -EBUSY;
 		/* Not necessarily safe to free, so leak it.. */
 		root_node = NULL;
-- 
2.47.3