On Thu, Apr 01, 2021 at 03:10:49PM -0700, Yu-cheng Yu wrote: > When serving a page fault, maybe_mkwrite() makes a PTE writable if its vma > has VM_WRITE. > > A shadow stack vma has VM_SHADOW_STACK. Its PTEs have _PAGE_DIRTY, but not > _PAGE_WRITE. In fork(), _PAGE_DIRTY is cleared to cause copy-on-write, > and in the page fault handler, _PAGE_DIRTY is restored and the shadow stack > page is writable again. > > Introduce an x86 version of maybe_mkwrite(), which sets proper PTE bits > according to VM flags. > > Apply the same changes to maybe_pmd_mkwrite(). > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > --- > v24: > - Instead of doing arch_maybe_mkwrite(), overwrite maybe*_mkwrite() with x86 > versions. > - Change VM_SHSTK to VM_SHADOW_STACK. > > arch/x86/include/asm/pgtable.h | 8 ++++++++ > arch/x86/mm/pgtable.c | 20 ++++++++++++++++++++ > include/linux/mm.h | 2 ++ > mm/huge_memory.c | 2 ++ > 4 files changed, 32 insertions(+) > > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 46d9394b884f..51cdf14488b7 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -1686,6 +1686,14 @@ static inline bool arch_faults_on_old_pte(void) > return false; > } > > +#define maybe_mkwrite maybe_mkwrite > +extern pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +#define maybe_pmd_mkwrite maybe_pmd_mkwrite > +extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma); > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ Move it next to other THP-depended stuff. Otherwise looks good to me: Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kirill A. Shutemov
