Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6

[mirror_ubuntu-artful-kernel.git] / mm / mremap.c

diff --git a/mm/mremap.c b/mm/mremap.c
index 6ccecc03f56ad05940484a481c5a092f1ad245ef..30d7d2482eea1d04cf72b03bcd54d1d293f666e4 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -149,14 +149,18 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
                if (pte_none(*old_pte))
                        continue;
 
+               pte = ptep_get_and_clear(mm, old_addr, old_pte);
                /*
-                * We are remapping a dirty PTE, make sure to
-                * flush TLB before we drop the PTL for the
+                * If we are remapping a dirty PTE, make sure
+                * to flush TLB before we drop the PTL for the
                 * old PTE or we may race with page_mkclean().
+                *
+                * This check has to be done after we removed the
+                * old PTE from page tables or another thread may
+                * dirty it after the check and before the removal.
                 */
-               if (pte_present(*old_pte) && pte_dirty(*old_pte))
+               if (pte_present(pte) && pte_dirty(pte))
                        force_flush = true;
-               pte = ptep_get_and_clear(mm, old_addr, old_pte);
                pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
                pte = move_soft_dirty_pte(pte);
                set_pte_at(mm, new_addr, new_pte, pte);