Re: [PATCH] mm: debug_page_alloc: fix NULL buf in debug_guardpage_minorder_setup

[John Hubbard]

On 8/5/26 5:45 PM, Ye Liu wrote:
> From: Ye Liu <liuye@xxxxxxxxxx>
> 
> If the kernel command line includes "debug_guardpage_minorder" without
> an equals sign (i.e., no value is provided), the early parameter
> parser passes a NULL buf pointer to the setup function.
> 
> kstrtouint() does not perform a NULL check on its input and calls
> directly into kstrtoull() which dereferences s[0] unconditionally,
> leading to a NULL pointer dereference and early boot crash.
> 
> Additionally, the error path's pr_err("%s", buf) would also crash with
> a NULL format argument.
> 

Maybe a "Fixes:" tag is called for?


> Signed-off-by: Ye Liu <liuye@xxxxxxxxxx>
> ---
>  mm/debug_page_alloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/debug_page_alloc.c b/mm/debug_page_alloc.c
> index 41e3d1f1ad96..fd2664c3c86a 100644
> --- a/mm/debug_page_alloc.c
> +++ b/mm/debug_page_alloc.c
> @@ -22,8 +22,8 @@ static int __init debug_guardpage_minorder_setup(char *buf)
>  {
>  	unsigned int res;
>  
> -	if (kstrtouint(buf, 10, &res) < 0 ||  res > MAX_PAGE_ORDER / 2) {
> -		pr_err("Bad debug_guardpage_minorder value: %s\n", buf);
> +	if (!buf || kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) {
> +		pr_err("Bad debug_guardpage_minorder value: %s\n", buf ?: "(missing)");
>  		return 0;
>  	}
>  	_debug_guardpage_minorder = res;

thanks,
-- 
John Hubbard