X-Git-Url: https://git.proxmox.com/?a=blobdiff_plain;f=mm%2Fmremap.c;h=30d7d2482eea1d04cf72b03bcd54d1d293f666e4;hb=e387dc122fc7c70c2a5df2567f4e2d1114f5a5da;hp=6ccecc03f56ad05940484a481c5a092f1ad245ef;hpb=c4364f837caf618c2fdb51a2e132cf29dfd1fffa;p=mirror_ubuntu-artful-kernel.git

diff --git a/mm/mremap.c b/mm/mremap.c
index 6ccecc03f56a..30d7d2482eea 100644
--- 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);