[PATCH v22 16/28] mm: Fixup places that call pte_mkwrite() directly

[Yu-cheng Yu]

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...@intel.com>
Reviewed-by: Kees Cook <keesc...@chromium.org>
---
 mm/memory.c   | 5 ++---
 mm/migrate.c  | 3 +--
 mm/mprotect.c | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index c8e357627318..0bdc6f2a8fe0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3559,8 +3559,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
        __SetPageUptodate(page);
 
        entry = mk_pte(page, vma->vm_page_prot);
-       if (vma->vm_flags & VM_WRITE)
-               entry = pte_mkwrite(pte_mkdirty(entry));
+       entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 
        vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
                        &vmf->ptl);
@@ -4123,7 +4122,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
        pte = pte_modify(old_pte, vma->vm_page_prot);
        pte = pte_mkyoung(pte);
        if (was_writable)
-               pte = pte_mkwrite(pte);
+               pte = maybe_mkwrite(pte, vma);
        ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
        update_mmu_cache(vma, vmf->address, vmf->pte);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 62b81d5257aa..7251c88a3d64 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2976,8 +2976,7 @@ static void migrate_vma_insert_page(struct migrate_vma 
*migrate,
                }
        } else {
                entry = mk_pte(page, vma->vm_page_prot);
-               if (vma->vm_flags & VM_WRITE)
-                       entry = pte_mkwrite(pte_mkdirty(entry));
+               entry = maybe_mkwrite(pte_mkdirty(entry), vma);
        }
 
        ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 94188df1ee55..c1ce78d688b6 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -135,7 +135,7 @@ static unsigned long change_pte_range(struct vm_area_struct 
*vma, pmd_t *pmd,
                        if (dirty_accountable && pte_dirty(ptent) &&
                                        (pte_soft_dirty(ptent) ||
                                         !(vma->vm_flags & VM_SOFTDIRTY))) {
-                               ptent = pte_mkwrite(ptent);
+                               ptent = maybe_mkwrite(ptent, vma);
                        }
                        ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
                        pages++;
-- 
2.21.0