Re: [PATCH v2 2/4] mm: mprotect: use walk_page_range_vma() in mprotect_fixup()

[Pedro Falcato <pfalcato@suse.de>]

On Thu, Jun 18, 2026 at 05:28:43PM +0800, Kefeng Wang wrote:
> In mprotect_fixup(), the PROT_NONE PFN permission check uses
> walk_page_range() to walk the page table. Fortunately, the caller
> always passes start/end that falls within a single VMA, the
> do_mprotect_pkey() iterates per-VMA via for_each_vma_range(),
> and setup_arg_pages() passes the whole VMA.
> 
> Note, walk_page_test() isn't called in walk_page_range_vma(),
> however, prot_none_test() in prot_none_walk_ops always return 0,
> so it's safe to replace walk_page_range() with walk_page_range_vma()
> to eliminate an unnecessary find_vma() lookup, also remove
> unneeded prot_none_test() too.

Again, I strongly prefer walk_page_range_vma() to be consistent with
walk_page_range() and others. But the change itself (apart from that)
is fairly uncontroversial, LGTM.

Reviewed-by: Pedro Falcato <pfalcato@suse.de>

> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  mm/mprotect.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 9cbf932b028c..b1595450e241 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -708,16 +708,9 @@ static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  		0 : -EACCES;
>  }
>  
> -static int prot_none_test(unsigned long addr, unsigned long next,
> -			  struct mm_walk *walk)
> -{
> -	return 0;
> -}
> -
>  static const struct mm_walk_ops prot_none_walk_ops = {
>  	.pte_entry		= prot_none_pte_entry,
>  	.hugetlb_entry		= prot_none_hugetlb_entry,
> -	.test_walk		= prot_none_test,
>  	.walk_lock		= PGWALK_WRLOCK,
>  };
>  
> @@ -753,7 +746,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
>  	    !vma_flags_test_any_mask(&new_vma_flags, VMA_ACCESS_FLAGS)) {
>  		pgprot_t new_pgprot = vm_get_page_prot(newflags);
>  
> -		error = walk_page_range(current->mm, start, end,
> +		error = walk_page_range_vma(vma, start, end,
>  				&prot_none_walk_ops, &new_pgprot);
>  		if (error)
>  			return error;
> -- 
> 2.27.0
> 
> 
> 

-- 
Pedro