Re: [PATCH v21 10/26] x86/mm: Update pte_modify for _PAGE_COW

[Borislav Petkov]

On Wed, Feb 17, 2021 at 02:27:14PM -0800, Yu-cheng Yu wrote:
> @@ -787,16 +802,34 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
>  	 */
>  	val &= _PAGE_CHG_MASK;
>  	val |= check_pgprot(newprot) & ~_PAGE_CHG_MASK;
> +	val = fixup_dirty_pte(val);

Do I see it correctly that you can do here and below:

	/*
	 * Fix up potential shadow stack page flags because the RO, Dirty PTE is
	 * special.
	 */
	if (pte_dirty()) {
		pte_mkclean();
		pte_mkdirty();
	}

?

That fixup thing looks grafted and not like a normal flow to me.

-- 
Regards/Gruss,
    Boris.

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