Hello,
As we know, it's not safe to use chroot() for resolving untrusted paths
within some root, as a subdirectory could be moved outside of the
process root while walking the path[1]. On the other hand,
LOOKUP_BENEATH is supposed to be robust against this, and going by [2],
it sounds like resolving with the mount namespace root as dirfd should
also be.
My question is: would resolving an untrusted path against a detached
mount root dirfd opened with OPEN_TREE_CLONE (not necessarily a
filesystem root) also be expected to be robust against traversal issues?
i.e. can I rely on an untrusted path never resolving to a path that
isn't under the mount root?
[1]: https://lore.kernel.org/lkml/CAG48ez30WJhbsro2HOc_DR7V91M+hNFzBP5ogRMZaxbAORvqzg@mail.gmail.com/ (local)
[2]: https://lore.kernel.org/lkml/C89D720F-3CC4-4FA9-9CBB-E41A67360A6B@amacapital.net/ (local)