1 files changed, 8 insertions, 1 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 8be2b144fefd..8583fb91ef13 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1270,8 +1270,15 @@ static int write_protect_page(struct vm_area_struct *vma, struct folio *folio,
 	if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?"))
 		goto out_unlock;
 
-	anon_exclusive = PageAnonExclusive(&folio->page);
 	entry = ptep_get(pvmw.pte);
+	/*
+	 * Handle PFN swap PTEs, such as device-exclusive ones, that actually
+	 * map pages: give up just like the next folio_walk would.
+	 */
+	if (unlikely(!pte_present(entry)))
+		goto out_unlock;
+
+	anon_exclusive = PageAnonExclusive(&folio->page);
 	if (pte_write(entry) || pte_dirty(entry) ||
 	    anon_exclusive || mm_tlb_flush_pending(mm)) {
 		swapped = folio_test_swapcache(folio);