tracefs: Add missing lockdown check to tracefs_create_dir()

The function tracefs_create_dir() was missing a lockdown check and was
called by the RV code. This gave an inconsistent behavior of this function
returning success while other tracefs functions failed. This caused the
inode being freed by the wrong kmem_cache.

Link: https://lkml.kernel.org/r/20230905182711.692687042@goodmis.org
Link: https://lore.kernel.org/all/202309050916.58201dc6-oliver.sang@intel.com/

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ajay Kaher <akaher@vmware.com>
Cc: Ching-lin Yu <chinglinyu@google.com>
Fixes: bf8e6021 ("tracing: Do not create tracefs files if tracefs lockdown is in effect")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fs/tracefs/inode.c

@@ -673,6 +673,9 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent,
  */
 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
 {
+	if (security_locked_down(LOCKDOWN_TRACEFS))
+		return NULL;
+
 	return __create_dir(name, parent, &simple_dir_inode_operations);
 }