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

[Song Liu]

On Wed, Jun 4, 2025 at 12:37 PM Song Liu <song at kernel.org> wrote:
>
> 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 just realized this only fails on hostfs. AFAICT, hostfs is only used
by um. Do we really need this to behave the same on um+hostfs?

Thanks,
Song

>
> 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