Filelock: UnixFileLock Truncates And Chmods Any Regular File Another User Renames Or Hard-links Onto The Lock Path

"UnixFileLock", the backend of "FileLock" and "AsyncFileLock" on Unix, empties whatever regular file it finds at the lock path once it holds the "flock" a kernel lock on an open file. With an explicit "mode" it also chmods that file sets its permission bits, whether or not this acquire created it...