[PATCH v2] of: fix incorrect device creation for reserved memory nodes

[Kenny Cheng]

The current global search for nodes in reserved_mem_matches can find
nodes outside "/reserved-memory". These nodes might not have actual
memory reserved (via memblock), leading to drivers (e.g., ramoops)
accessing unreserved memory and causing memory corruption.

Prioritize scanning children of "/reserved-memory" to ensure the device
is backed by reserved memory. A fallback is kept for compatibility.
Proper reference counting is also added.

Signed-off-by: Kenny Cheng <chao.shun.cheng.tw@xxxxxxxxx>
---
v2:
  - Fix missing variable declaration for 'reserved'.
---
 drivers/of/platform.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index ba591fbceb56..68bba234cbea 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -500,7 +500,7 @@ static const struct of_device_id reserved_mem_matches[] = {
 
 static int __init of_platform_default_populate_init(void)
 {
-	struct device_node *node;
+	struct device_node *node, *reserved;
 
 	device_links_supplier_sync_state_pause();
 
@@ -563,8 +563,17 @@ static int __init of_platform_default_populate_init(void)
 		 * platform_devices for every node in /reserved-memory with a
 		 * "compatible",
 		 */
-		for_each_matching_node(node, reserved_mem_matches)
-			of_platform_device_create(node, NULL, NULL);
+		reserved = of_find_node_by_path("/reserved-memory");
+		if (reserved) {
+			for_each_child_of_node(reserved, node) {
+				if (of_match_node(reserved_mem_matches, node))
+					of_platform_device_create(node, NULL, NULL);
+			}
+			of_node_put(reserved);
+		} else {
+			for_each_matching_node(node, reserved_mem_matches)
+				of_platform_device_create(node, NULL, NULL);
+		}
 
 		node = of_find_node_by_path("/firmware");
 		if (node) {
-- 
2.34.1