Re: [PATCH v25 16/30] mm: Fixup places that call pte_mkwrite() directly

[Kirill A. Shutemov]

On Thu, Apr 15, 2021 at 03:14:05PM -0700, Yu-cheng Yu wrote:
> When serving a page fault, maybe_mkwrite() makes a PTE writable if it is in
> a writable vma.  A shadow stack vma is writable, but its PTEs need
> _PAGE_DIRTY to be set to become writable.  For this reason, maybe_mkwrite()
> has been updated.
> 
> There are a few places that call pte_mkwrite() directly, but have the
> same result as from maybe_mkwrite().  These sites need to be updated for
> shadow stack as well.  Thus, change them to maybe_mkwrite():
> 
> - do_anonymous_page() and migrate_vma_insert_page() check VM_WRITE directly
>   and call pte_mkwrite(), which is the same as maybe_mkwrite().  Change
>   them to maybe_mkwrite().
> 
> - In do_numa_page(), if the numa entry was writable, then pte_mkwrite()
>   is called directly.  Fix it by doing maybe_mkwrite().  Make the same
>   changes to do_huge_pmd_numa_page().
> 
> - In change_pte_range(), pte_mkwrite() is called directly.  Replace it with
>   maybe_mkwrite().
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

-- 
 Kirill A. Shutemov