On Tue, Jun 3, 2025 at 6:46 AM Mickaël Salaün [off-list ref] 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