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

Borislav Petkov
2021-03-05T14:30:28Z

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.