[PATCH v5 8/9] of/overlay: rewrite /aliases path values to live-tree paths

[Abdurrahman Hussain]

An /aliases property added by an overlay references labeled nodes as
"&label", which dtc renders as an overlay-internal path such as
"/fragment@1/__overlay__/i2c@40000". The value is copied verbatim
into the live tree, of_find_node_by_path() cannot resolve it, and
of_alias_get_id() keeps returning -ENODEV.

/__symbols__ values follow the same convention and are already
rewritten by dup_and_fixup_symbol_prop(). Use it for properties of
the /aliases node too:

  - a value that resolves inside one of the overlay's fragments is
    stored rewritten to the live-tree path
  - -ENODEV (legacy string aliases, absolute live-tree paths) is
    copied verbatim, as before this series
  - -EINVAL (not a NUL-terminated string) is copied verbatim with a
    warning; consumers validate before dereferencing, and an overlay
    that applied before this series keeps applying
  - only -ENOMEM fails the apply

Pseudo-properties are exempt: the is_pseudo_property() check at the
top of add_changeset_property() only covers live-tree targets, and a
phandle of a newly created /aliases node is a cell, not a string.

Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
---
 drivers/of/overlay.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 1a2df83fbd8d..27a460daeed9 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -370,6 +370,19 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
 		if (IS_ERR(new_prop))
 			return PTR_ERR(new_prop);
+	} else if (!is_pseudo_property(overlay_prop->name) &&
+		   of_node_is_aliases(target->np)) {
+		/* rewrite overlay-internal alias values to live-tree paths */
+		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+		if (new_prop == ERR_PTR(-ENOMEM))
+			return -ENOMEM;
+		if (IS_ERR(new_prop)) {
+			if (new_prop == ERR_PTR(-EINVAL))
+				pr_warn("%pOF/%s is not a valid string; alias will be inert\n",
+					target->np, overlay_prop->name);
+			/* not overlay-internal: copy verbatim, consumers validate */
+			new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
+		}
 	} else {
 		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	}

-- 
2.54.0