chroot alternative for threads

Question

I know that you can't technically chroot a thread, but I'm looking for functional alternatives that would limit the amount of permissions to an existing set of tasks within a thread.

Edit: This is for a Linux environment, however Windows related techniques would be useful as well (even if they have no *NIX equivalent.

Answer 1

There are few differences between threads and processes on Linux. Use the clone syscall with the flag CLONE_THREAD and without the flag CLONE_FS, so that the new thread does not share its root directory/current directory/umask with the calling thread. Alternatively, you can use the unshare syscall with CLONE_FS after the fact. Now you can use chroot as normal and it will not affect other threads in the process.