[LTP] [RFC PATCH] landlock: fix minimal required size for landlock_ruleset_attr copying

[Li Wang]

On Tue, Jul 2, 2024 at 9:00 PM Mickaël Salaün <mic@digikod.net> wrote:

> On Tue, Jul 02, 2024 at 05:47:45PM +0800, Li Wang wrote:
> > As kernel commit fff69fb03dde ("landlock: Support network rules with TCP
> bind and connect")
> > introducing a new field 'handled_access_net' in the structure
> landlock_ruleset_attr,
> > but in the landlock_create_ruleset() it still uses the first field
> 'handled_access_fs'
> > to calculate minimal size, so that made decrease 1 is useless in LTP
> landlock01.c to
> > test the too-small-size.
> >
> > Test code:
> >    rule_small_size = sizeof(struct landlock_ruleset_attr) - 1;
> >    tst_syscall(__NR_landlock_create_ruleset, ..., rule_small_size, 0)
> >
> > Result:
> >   landlock01.c:49: TFAIL: Size is too small expected EINVAL: ENOMSG (42)
>
> Interesting, this looks like a bug in these LTP tests.
>

Yes, Andrea drafted a series of landlock tests for LTP.

FYI -
https://patchwork.ozlabs.org/project/ltp/list/?series=&submitter=&state=&q=landlock&archive=&delegate=



>
> >
> > Signed-off-by: Li Wang <liwang@redhat.com>
> > Cc: Mickaël Salaün <mic@digikod.net>
> > Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
> > Cc: Paul Moore <paul@paul-moore.com>
> > ---
> >
> > Notes:
> >     Hi Mickael,
> >        I'm not quite sure if that is on purpose to use the first field
> or kernel
> >        bug, can you take a look?
>
> Hi Li,
>
> Yes this is on purpose.  The handled_access_fs minimal size check should
> never change for backward compatibility reason.  User space built with
> old headers must still work with new kernels.  This is tested with the
> "inconsistent_attr" test in tools/testing/selftests/landlock/base_test.c
>

Thanks for the confirmation, very helpful.

@Andrea Cervesato <acervesato@suse.de>, seems we have to adjust the test to
use a real small
rule size which is at least small than sizeof(__u64).


-- 
Regards,
Li Wang