filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted symlink or journal file makes the lock user's process overwrite or unlink its own files

ReadWriteLock and AsyncReadWriteLock the SQLite-backed reader/writer lock hand SQLite a name they do not control. On Linux the lock validates its database through a descriptor the number the kernel gives a process for an open file. It then connects SQLite to /proc/self/fd/, a Linux path that name...