TYPO3 Core

How can I search for files or folders with invalid UTF-8 encoding?

If somebody is facing the same problem like me, here is a easy way to find the folders or files with invalid encoded names:
Insert at the beginning of the validPathStr function in sysext/core/Classes/Utility/GeneralUtility.php:

if(!(preg_match('#(?:^\\.\\.|/\\.\\./|[[:cntrl:]])#u', $theFile) === 0)) {
  echo $theFile."<br>";
}

Edit a filemount where the error occured and you should see the list of the folders or files with invalid encoding.
If it's not possible to correct the names using the filelist module, do it on a system level.
Don't forget to revert the code changes.