Re: [PATCH testsuite] selinux-testsuite: Add submount test

[Ondrej Mosnacek <omosnace@redhat.com>]

On Thu, Oct 10, 2019 at 12:50 AM Paul Moore <paul@paul-moore.com> wrote:
> On Wed, Oct 9, 2019 at 10:53 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > On Wed, Oct 9, 2019 at 4:01 PM Paul Moore <paul@paul-moore.com> wrote:
> > > On Wed, Oct 9, 2019 at 9:53 AM Stephen Smalley <sds@tycho.nsa.gov> wrote:
> > > > On 10/8/19 5:30 PM, Paul Moore wrote:
> > > > > On Mon, Sep 30, 2019 at 10:07 AM Stephen Smalley <sds@tycho.nsa.gov> wrote:
> > > > >> On 9/30/19 9:16 AM, Ondrej Mosnacek wrote:
> > > > >>> Add a test that verifies that SELinux permissions are not checked when
> > > > >>> mounting submounts. The test sets up a simple local NFS export on a
> > > > >>> directory which has another filesystem mounted on its subdirectory.
> > > > >>> Since the export is set up with the crossmnt option enabled, any client
> > > > >>> mount will try to transparently mount any subdirectory that has a
> > > > >>> filesystem mounted on it on the server, triggering an internal mount.
> > > > >>> The test tries to access the automounted part of this export via a
> > > > >>> client mount without having a permission to mount filesystems, expecting
> > > > >>> it to succeed.
> > > > >>>
> > > > >>> The original bug this test is checking for has been fixed in kernel
> > > > >>> commit 892620bb3454 ("selinux: always allow mounting submounts"), which
> > > > >>> has been backported to 4.9+ stable kernels.
> > > > >>>
> > > > >>> The test first checks whether it is able to export and mount directories
> > > > >>> via NFS and skips the actual tests if e.g. NFS daemon is not running.
> > > > >>> This means that the testsuite can still be run without having the NFS
> > > > >>> server installed and running.
> > > > >>
> > > > >> 1) We have to manually start nfs-server in order for the test to run;
> > > > >> else it will be skipped automatically.  Do we want to start/stop the
> > > > >> nfs-server as part of the test script?
> > > > >
> > > > > My two cents are that I'm not sure we want to automatically start/stop
> > > > > the NFS server with the usual "make test", perhaps we have a dedicated
> > > > > NFS test target that does the setup-test-shutdown?  Other ideas are
> > > > > welcome.
> > > >
> > > > I guess my concern is that anything that doesn't run with the default
> > > > make test probably won't get run at all with any regularity.
> > >
> > > FWIW, I think I'm the only one regularly running the tests on upstream
> > > kernels and reporting the results.  RH was running the tests at one
> > > point, and may still be doing so, but I have no idea what kernels they
> > > are testing (maybe just RHEL, stable Fedora, etc.) and what their
> > > process is when they find failures.
> >
> > We do still run the selinux-testsuite nightly on Fedora Rawhide with
> > your kernel-secnext kernel builds (I suppose we fetch them from COPR).
> > I can't really describe what we do when they fail, because that hardly
> > ever happens now :)
>
> I'm happy to hear that the tests are still running, but we must be
> looking at different test results ;)

Well, we pin the testsuite to a fixed commit and bump it manually as
needed/wanted, so we generally don't see failures that are fixed
quickly. But I don't recall many (non-false-positive) failures
appearing on kernel-secnext in the past few months either.

>
> > But if we came across a failure that would suggest
> > a bug, we would certainly investigate and report it.
>
> Great, thank you.
>
> > The testsuite is now also being run as part of CKI
> > (https://github.com/cki-project), which AFAIK currently runs regularly
> > on linux-stable kernels (the results are posted publicly to
> > stable@vger.kernel.org). I don't follow these reports closely, so I'm
> > not sure if there were any non-false-positive failures there...
>
> That's good news.  I assume CKI has some provision for emailing people
> when there are test failures?  I don't really need to see every
> -stable kernel test, but it might be nice to see the failures.
> Alternatively, now that I think about it, this shouldn't be that hard
> to setup with the secnext stuff ...

I don't know if it is possible to subscribe to test failures (I'd
guess not). There is a notion of test maintainers, who are defined
internally, who receive reports of failures for review before they are
sent to relevant recipients, but this is an internal-only facility...
Maybe you can try filing a feature request at [1]?

[1] https://github.com/CKI-project/meta/issues

>
> > > > For
> > > > something that requires specialized hardware (e.g. InfiniBand), this is
> > > > reasonable but that isn't true of NFS.  For the more analogous cases of
> > > > e.g. labeled IPSEC, NetLabel, SECMARK, we already load and unload
> > > > network configurations for the testsuite during testing.
> > >
> > > That's a good point about the other networking tests.  My gut feeling
> > > tells me that NFS should be "different", but I guess I can't really
> > > justify that statement in an objectively meaningful way.
> >
> > I think the main reason why I didn't include NFS server starting was
> > that I don't know how to do it robustly across distros... Already on
> > RHEL the service name varies ("nfs-server" vs. just "nfs") and then
> > there is "service xyz start" vs. "systemctl start xyz"...
>
> That's another good point.  At this point in time I think it is
> relatively safe to stick with systemd/systemctl (and skip if systemctl
> is not found) as systemd appears to be eating the world; although this
> doesn't help with the service name problem.

It seems that wherever the service can be started by systemctl, it is
called "nfs-server" (on RHEL-7 there is also an alias "nfs"), so I
think we can stick to just 'systemctl start nfs-server' and it should
work most (if not all) of the time.

--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.