I am developing FS to do some nasty tasks. It would restrict file access. It will asks user about he/she allows file open/create/move/removal/etc.

I create executable with set group id. Because user must mount FS, I mount as user and next change group id to access protected directory.

Problem is I cannot protect from unmount operation. Some bad guy could unmount FS and perform normal file operations, so if user mount some protected directory to ~/bin (for example), someone could unmount from ~/bin and write custom executable to ~/bin. The same about config files.

What I trying to do is to remove this piece of code:

    if (fuse_set_signal_handlers(session) != 0) {
      goto end1;
    }

And write something like this:

    do {
      (void) fuse_session_loop_mt(session, &config);
    } while (!grant_access(OP_UNMOUNT, NULL, NULL));
    fuse_session_unmount(session);
    fuse_session_destroy(session);

But this do not work. I use libfuse in version 3 and low-level libfuse API.