[PATCH] cmd: extension: Fix possible null pointer dereference

[Quentin Schulz]

Hi Köry,

On 11/12/25 2:07 PM, Kory Maincent wrote:
> From: "Kory Maincent (TI.com)" <kory.maincent at bootlin.com>
> 
> Add a null check for extension_list before calling alist_get_ptr() to
> prevent a potential null pointer dereference. If extension_get_list()
> returns NULL, alist_get_ptr() would attempt to dereference it, leading
> to undefined behavior.
> 
> The fix ensures both extension_list and its first element are checked
> before proceeding with the list operation.
> 
> Closes: https://lists.denx.de/pipermail/u-boot/2025-November/602892.html
> Fixes: 2d12958ee71b ("boot: Remove legacy extension board support")
> Signed-off-by: Kory Maincent (TI.com) <kory.maincent at bootlin.com>
> ---
>   cmd/extension_board.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/cmd/extension_board.c b/cmd/extension_board.c
> index 86e4795ba8a..1b92be82611 100644
> --- a/cmd/extension_board.c
> +++ b/cmd/extension_board.c
> @@ -99,7 +99,7 @@ static int do_extension_list(struct cmd_tbl *cmdtp, int flag,
>   	int i = 0;
>   
>   	extension_list = extension_get_list();
> -	if (!alist_get_ptr(extension_list, 0)) {
> +	if (!extension_list || !alist_get_ptr(extension_list, 0)) {

Is it possible that one runs extension scan which returns no supported 
extension (alist_empty(), the default state before calling the scan() 
ops for the extension uclass driver)?

In which case, we should only check whether extension_list is NULL and 
not whether there's at least one extension?

Or at least have a different error code between "scan wasn't run" and 
"scan returned no extension", if that is a distinction we can make?

Cheers,
Quentin