[PATCH v4 4/6] of/overlay: return ERR_PTR from dup_and_fixup_symbol_prop()

[Abdurrahman Hussain]

dup_and_fixup_symbol_prop() returns NULL for three very different
reasons: the property value is not a valid non-empty C string
(malformed input), the value does not resolve to a node inside one of
the overlay's fragments (not an overlay-internal path), and memory
allocation failure. Its only caller today reports every NULL as
-ENOMEM, so structural problems in an overlay's /__symbols__ node are
diagnosed as memory exhaustion.

The next patch reuses the helper for /aliases values, where the
distinction is load-bearing: a value that doesn't resolve inside the
overlay is a legacy alias that must be copied verbatim, a malformed
value must be admitted inertly with a warning, and only a real
allocation failure may fail the overlay apply.

Return ERR_PTR instead: -EINVAL for malformed values, -ENODEV when
the value is not a path into one of the overlay's fragments, -ENOMEM
for allocation failures. The /__symbols__ caller now propagates the
distinct errno instead of collapsing everything to -ENOMEM.

Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
---
 drivers/of/overlay.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 74aea704835a..ad4e50482515 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -206,6 +206,10 @@ static void overlay_fw_devlink_refresh(struct overlay_changeset *ovcs)
  * The duplicated property value will be modified by replacing the
  * "/fragment_name/__overlay/" portion of the value  with the target
  * path from the fragment node.
+ *
+ * Return: the fixed-up property, or ERR_PTR: -EINVAL if @prop's value
+ * is not a valid non-empty C string, -ENODEV if it is not a path into
+ * one of @ovcs's fragments, -ENOMEM on allocation failure.
  */
 static struct property *dup_and_fixup_symbol_prop(
 		struct overlay_changeset *ovcs, const struct property *prop)
@@ -224,14 +228,14 @@ static struct property *dup_and_fixup_symbol_prop(
 	int target_path_len;
 
 	if (!prop->value)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	if (strnlen(prop->value, prop->length) >= prop->length)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	path = prop->value;
 	path_len = strlen(path);
 
 	if (path_len < 1)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	fragment_node = __of_find_node_by_path(ovcs->overlay_root, path + 1);
 	overlay_node = __of_find_node_by_path(fragment_node, "__overlay__/");
 	of_node_put(fragment_node);
@@ -243,18 +247,18 @@ static struct property *dup_and_fixup_symbol_prop(
 			break;
 	}
 	if (k >= ovcs->count)
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	overlay_name_len = snprintf(NULL, 0, "%pOF", fragment->overlay);
 
 	if (overlay_name_len > path_len)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	path_tail = path + overlay_name_len;
 	path_tail_len = strlen(path_tail);
 
 	target_path = kasprintf(GFP_KERNEL, "%pOF", fragment->target);
 	if (!target_path)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	target_path_len = strlen(target_path);
 
 	new_prop = kzalloc_obj(*new_prop);
@@ -281,7 +285,7 @@ static struct property *dup_and_fixup_symbol_prop(
 err_free_target_path:
 	kfree(target_path);
 
-	return NULL;
+	return ERR_PTR(-ENOMEM);
 }
 
 /**
@@ -350,6 +354,8 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 		if (prop)
 			return -EINVAL;
 		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+		if (IS_ERR(new_prop))
+			return PTR_ERR(new_prop);
 	} else {
 		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	}

-- 
2.54.0