On Wed, Feb 03, 2021 at 02:55:37PM -0800, 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 effect 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(). > > - In change_pte_range(), pte_mkwrite() is called directly. Replace it with > maybe_mkwrite(). > > A shadow stack vma is writable but has different vma > flags, and handled accordingly in maybe_mkwrite(). > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
