[PATCH v2 bpf-next 2/4] landlock: Use path_walk_parent()

[Song Liu]

On Tue, Jun 3, 2025 at 6:46 AM Mickaël Salaün <mic at digikod.net> wrote:
>
> Landlock tests with hostfs fail:
>
> ok 126 layout3_fs.hostfs.tag_inode_file
> #  RUN           layout3_fs.hostfs.release_inodes ...
> # fs_test.c:5555:release_inodes:Expected EACCES (13) == test_open(TMP_DIR, O_RDONLY) (0)
>
> This specific test checks that an access to a (denied) mount point over
> an allowed directory is indeed denied.

I am having trouble understanding the test. It appears to me
the newly mounted tmpfs on /tmp is allowed, but accesses to
/ and thus mount point /tmp is denied? What would the walk in
is_access_to_paths_allowed look like?

> It's not clear to me the origin of the issue, but it seems to be related
> to choose_mountpoint().
>
> You can run these tests with `check-linux.sh build kselftest` from
> https://github.com/landlock-lsm/landlock-test-tools

How should I debug this test? printk doesn't seem to work.

Thanks,
Song