The whitelist approach looks good to me. (I first wondered whether it would be possible to first mount a FUSE filesystem over /proc/$pid, then mount an ecryptfs over that, but that wouldn't work because unprivileged FUSE wouldn't allow the chdir() to the filesystem root.)
The whitelist approach looks good to me. (I first wondered whether it would be possible to first mount a FUSE filesystem over /proc/$pid, then mount an ecryptfs over that, but that wouldn't work because unprivileged FUSE wouldn't allow the chdir() to the filesystem root.)