---

yaml
---
r: 210154
b: refs/heads/master
c: 7a2e8a8
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2bfc96a127bc1cc94d26bfaa40159966064f9c8c
+refs/heads/master: 7a2e8a8faab76386d8eaae9ded739ee5615be174

trunk/fs/namespace.c

@@ -1483,14 +1483,31 @@ static int graft_tree(struct vfsmount *mnt, struct path *path)
 	return err;
 }
 
+/*
+ * Sanity check the flags to change_mnt_propagation.
+ */
+
+static int flags_to_propagation_type(int flags)
+{
+	int type = flags & ~MS_REC;
+
+	/* Fail if any non-propagation flags are set */
+	if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+		return 0;
+	/* Only one propagation flag should be set */
+	if (!is_power_of_2(type))
+		return 0;
+	return type;
+}
+
 /*
  * recursively change the type of the mountpoint.
  */
 static int do_change_type(struct path *path, int flag)
 {
 	struct vfsmount *m, *mnt = path->mnt;
 	int recurse = flag & MS_REC;
-	int type = flag & ~MS_REC;
+	int type;
 	int err = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -1499,6 +1516,10 @@ static int do_change_type(struct path *path, int flag)
 	if (path->dentry != path->mnt->mnt_root)
 		return -EINVAL;
 
+	type = flags_to_propagation_type(flag);
+	if (!type)
+		return -EINVAL;
+
 	down_write(&namespace_sem);
 	if (type == MS_SHARED) {
 		err = invent_group_ids(mnt, recurse);