1 files changed, 30 insertions, 17 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index bd601ab26e78..bb1560b0d25c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -747,15 +747,11 @@ int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
 		return 0;
 	mnt = real_mount(bastard);
 	mnt_add_count(mnt, 1);
-	smp_mb();			// see mntput_no_expire()
+	smp_mb();		// see mntput_no_expire() and do_umount()
 	if (likely(!read_seqretry(&mount_lock, seq)))
 		return 0;
-	if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
-		mnt_add_count(mnt, -1);
-		return 1;
-	}
 	lock_mount_hash();
-	if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
+	if (unlikely(bastard->mnt_flags & (MNT_SYNC_UMOUNT | MNT_DOOMED))) {
 		mnt_add_count(mnt, -1);
 		unlock_mount_hash();
 		return 1;
@@ -1916,6 +1912,7 @@ static int do_umount(struct mount *mnt, int flags)
 			umount_tree(mnt, UMOUNT_PROPAGATE);
 		retval = 0;
 	} else {
+		smp_mb(); // paired with __legitimize_mnt()
 		shrink_submounts(mnt);
 		retval = -EBUSY;
 		if (!propagate_mount_busy(mnt, 2)) {
@@ -2266,6 +2263,11 @@ struct vfsmount *clone_private_mount(const struct path *path)
 	if (!check_mnt(old_mnt))
 		goto invalid;
 
+	if (!ns_capable(old_mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) {
+		up_read(&namespace_sem);
+		return ERR_PTR(-EPERM);
+	}
+
 	if (has_locked_children(old_mnt, path->dentry))
 		goto invalid;
 
@@ -2524,14 +2526,14 @@ static int attach_recursive_mnt(struct mount *source_mnt,
 	hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
 		struct mount *q;
 		hlist_del_init(&child->mnt_hash);
-		q = __lookup_mnt(&child->mnt_parent->mnt,
-				 child->mnt_mountpoint);
-		if (q)
-			mnt_change_mountpoint(child, smp, q);
 		/* Notice when we are propagating across user namespaces */
 		if (child->mnt_parent->mnt_ns->user_ns != user_ns)
 			lock_mnt_tree(child);
 		child->mnt.mnt_flags &= ~MNT_LOCKED;
+		q = __lookup_mnt(&child->mnt_parent->mnt,
+				 child->mnt_mountpoint);
+		if (q)
+			mnt_change_mountpoint(child, smp, q);
 		commit_tree(child);
 	}
 	put_mountpoint(smp);
@@ -2717,6 +2719,10 @@ static int do_change_type(struct path *path, int ms_flags)
 		return -EINVAL;
 
 	namespace_lock();
+	if (!check_mnt(mnt)) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
 	if (type == MS_SHARED) {
 		err = invent_group_ids(mnt, recurse);
 		if (err)
@@ -3154,7 +3160,7 @@ static int do_set_group(struct path *from_path, struct path *to_path)
 	if (IS_MNT_SLAVE(from)) {
 		struct mount *m = from->mnt_master;
 
-		list_add(&to->mnt_slave, &m->mnt_slave_list);
+		list_add(&to->mnt_slave, &from->mnt_slave);
 		to->mnt_master = m;
 	}
 
@@ -3179,18 +3185,25 @@ out:
  * Check if path is overmounted, i.e., if there's a mount on top of
  * @path->mnt with @path->dentry as mountpoint.
  *
- * Context: This function expects namespace_lock() to be held.
+ * Context: namespace_sem must be held at least shared.
+ * MUST NOT be called under lock_mount_hash() (there one should just
+ * call __lookup_mnt() and check if it returns NULL).
  * Return: If path is overmounted true is returned, false if not.
  */
 static inline bool path_overmounted(const struct path *path)
 {
+	unsigned seq = read_seqbegin(&mount_lock);
+	bool no_child;
+
 	rcu_read_lock();
-	if (unlikely(__lookup_mnt(path->mnt, path->dentry))) {
-		rcu_read_unlock();
-		return true;
-	}
+	no_child = !__lookup_mnt(path->mnt, path->dentry);
 	rcu_read_unlock();
-	return false;
+	if (need_seqretry(&mount_lock, seq)) {
+		read_seqlock_excl(&mount_lock);
+		no_child = !__lookup_mnt(path->mnt, path->dentry);
+		read_sequnlock_excl(&mount_lock);
+	}
+	return unlikely(!no_child);
 }
 
 /**