check privileges before setting mount propagation

There's a missing check for CAP_SYS_ADMIN in do_change_type().
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/namespace.c

@@ -886,6 +886,9 @@ static int do_change_type(struct nameidata *nd, int flag)
 	int recurse = flag & MS_REC;
 	int type = flag & ~MS_REC;
 
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
 	if (nd->dentry != nd->mnt->mnt_root)
 		return -EINVAL;