Re: [PATCH 2/2] mm/vmalloc: warn on NULL page in remap_vmalloc_range_partial

["Jose A. Perez de Azpillaga" <azpijr@gmail.com>]

On 10/26/26 7:09 AM, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
> 
> remap_vmalloc_range_partial() oopses if vmalloc_to_page() returns
> NULL, which never happens today because VM_USERMAP areas keep every
> page mapped. Add a WARN_ON(!page) to flag a break before the oops.
> 
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  mm/vmalloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a888eca016a8..59ba203a4eff 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -4906,6 +4906,7 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
>  		struct page *page = vmalloc_to_page(kaddr);
>  		int ret;
>  
> +		WARN_ON(!page);
>  		ret = vm_insert_page(vma, uaddr, page);

doesn't this still hand the NULL page to vm_insert_page() right after,
so we warn and then oops anyway? wouldn't something like this be what
you want here?

		if (WARN_ON_ONCE(!page))
			return -EINVAL;

-- 
cheers,
jose a. p-a