FileSystem::mkdir generates SegFault on empty dir

[edit] FileSystemInterface::prepareDirectory => FileSystem::mkdir

There are other cases that do not trigger recursion but give strange results:

drush ev '$f = Drupal::service("file_system");$dir="........";var_dump($f->mkdir($dir, NULL, TRUE));'
drush ev '$f = Drupal::service("file_system");$dir="  ";var_dump($f->mkdir($dir, NULL, TRUE));'
ls -la web/
drwxrwxrwx  2 www-data www-data    6 Jun  5 15:50 ........
drwxrwxrwx  2 www-data www-data    6 Jun  5 15:50 '  '

I will provide a MR that avoid the recursion, but feel free to propose other checks.

this part seems to have rewritten in 11.x, can someone check if this is still an issue?

This bug was introduce by patch 54 on issue https://www.drupal.org/project/drupal/issues/2799635 🐛 FileSystem::mkdir should handle open_basedir correctly Needs work