2 files changed, 8 insertions, 3 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index da9990a..9ec50a3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -774,10 +774,8 @@ again:			remove_next = 1 + (end > next->vm_end);
 
 			importer->anon_vma = exporter->anon_vma;
 			error = anon_vma_clone(importer, exporter);
-			if (error) {
-				importer->anon_vma = NULL;
+			if (error)
 				return error;
-			}
 		}
 	}
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 5e3e090..c161a14 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -287,6 +287,13 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
 	return 0;
 
  enomem_failure:
+	/*
+	 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
+	 * decremented in unlink_anon_vmas().
+	 * We can safely do this because callers of anon_vma_clone() don't care
+	 * about dst->anon_vma if anon_vma_clone() failed.
+	 */
+	dst->anon_vma = NULL;
 	unlink_anon_vmas(dst);
 	return -ENOMEM;
 }