Notes:

Keep in mind that the result will be cached by system!

If you set read error with a probability < 1, once the program reads successfully, no error will be returned until the cache misses. If you override the attributes with a probability < 1, the first lookup may decide the attributes for a long time (until the cache misses).

But if you set probability == 1, which means the result will be the same all the time during the mount, there will be no problem.
Compile this binary with -Z relro-level=full, then it will load (mmap) all dependencies into memory at the beginning.
This program should be executed inside the target pid and mnt namespace

Known Issues