Subject: [PATCH v3 05/11] of: reserved_mem: split alloc_reserved_mem_array() from fdt_scan_reserved_mem_late()

From: Wandun Chen <[email-masked]>
Date: Wed, 27 May 2026 11:29:11 +0800

From: Wandun Chen <[email-masked]>

Prepare for storing /memreserve/ entries in the reserved_mem array.
alloc_reserved_mem_array is skipped if the device tree lacks a
/reserved-memory node, pointer 'reserved_mem' continues to reference
the reserved_mem_array which lives in __initdata, storing
/memreserve/ entries into reserved_mem_array would result in metadata
loss, and an out-of-bounds memory access will occur if the device
tree contains more than MAX_RESERVED_REGIONS /memreserve/ entries.

So split alloc_reserved_mem_array() from fdt_scan_reserved_mem_late(),
and call alloc_reserved_mem_array() whether or not there is a
/reserved-memory node.

No functional change.
The actual /memreserve/ population is added in a follow-up patch.

Signed-off-by: Wandun Chen <[email-masked]>
---
 drivers/of/fdt.c             | 7 +++++--
 drivers/of/of_private.h      | 1 +
 drivers/of/of_reserved_mem.c | 6 +-----
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 82f7327c59ea..83a2a474831e 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1284,8 +1284,11 @@ void __init unflatten_device_tree(void)
 {
 	void *fdt = initial_boot_params;
 
-	/* Save the statically-placed regions in the reserved_mem array */
-	fdt_scan_reserved_mem_late();
+	/* Attempt dynamic allocation of a new reserved_mem array */
+	if (fdt && alloc_reserved_mem_array()) {
+		/* Save the statically-placed regions in the reserved_mem array */
+		fdt_scan_reserved_mem_late();
+	}
 
 	/* Populate an empty root node when bootloader doesn't provide one */
 	if (!fdt) {
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index 0ae16da066e2..50e5a533e059 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -187,6 +187,7 @@ static inline struct device_node *__of_get_dma_parent(const struct device_node *
 
 int fdt_scan_reserved_mem(void);
 void __init fdt_scan_reserved_mem_late(void);
+bool __init alloc_reserved_mem_array(void);
 
 bool of_fdt_device_is_available(const void *blob, unsigned long node);
 
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 05defc91e901..888dcb6bdce5 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -69,7 +69,7 @@ static int __init early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
  * the initial static array is copied over to this new array and
  * the new array is used from this point on.
  */
-static bool __init alloc_reserved_mem_array(void)
+bool __init alloc_reserved_mem_array(void)
 {
 	struct reserved_mem *new_array;
 	size_t alloc_size, copy_size, memset_size;
@@ -272,10 +272,6 @@ void __init fdt_scan_reserved_mem_late(void)
 		return;
 	}
 
-	/* Attempt dynamic allocation of a new reserved_mem array */
-	if (!alloc_reserved_mem_array())
-		return;
-
 	if (__reserved_mem_check_root(node)) {
 		pr_err("Reserved memory: unsupported node format, ignoring\n");
 		return;
-- 
2.43.0