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

[Rob Herring <robh@kernel.org>]

On Wed, May 27, 2026 at 11:29:11AM +0800, Wandun Chen wrote:
> From: Wandun Chen <chenwandun@lixiang.com>
> 
> 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 <chenwandun@lixiang.com>
> ---
>  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();

Can we make this just:

alloc_reserved_mem_array();
fdt_scan_reserved_mem_late();

We already check !fdt in fdt_scan_reserved_mem_late().

Rob