linux-kernel - Re: [PATCH net-next v6 09/11] seccomp: Enhance test

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Message-ID: <CAGXu5j+D-FP8Kt9unNOqKrQJP4DYTpmgkJxWykZyrYiVPz3Y3Q@mail.gmail.com>
Date:   Tue, 18 Apr 2017 17:02:57 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Jann Horn <jann@...jh.net>, Jonathan Corbet <corbet@....net>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <shuah@...nel.org>, Tejun Heo <tj@...nel.org>,
        Thomas Graf <tgraf@...g.ch>, Will Drewry <wad@...omium.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v6 09/11] seccomp: Enhance test_harness with an
 assert step mechanism

On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@...ikod.net> wrote:
> This is useful to return an information about the error without being
> able to write to TH_LOG_STREAM.
>
> Helpers from test_harness.h may be useful outside of the seccomp
> directory.
>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Will Drewry <wad@...omium.org>
> ---
>  tools/testing/selftests/seccomp/test_harness.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/seccomp/test_harness.h b/tools/testing/selftests/seccomp/test_harness.h
> index a786c69c7584..77e407663e06 100644
> --- a/tools/testing/selftests/seccomp/test_harness.h
> +++ b/tools/testing/selftests/seccomp/test_harness.h
> @@ -397,7 +397,7 @@ struct __test_metadata {
>         const char *name;
>         void (*fn)(struct __test_metadata *);
>         int termsig;
> -       int passed;
> +       __s8 passed;

Why the reduction here? int is signed too?

>         int trigger; /* extra handler after the evaluation */
>         struct __test_metadata *prev, *next;
>  };
> @@ -476,6 +476,12 @@ void __run_test(struct __test_metadata *t)
>                                         "instead of by signal (code: %d)\n",
>                                         t->name,
>                                         WEXITSTATUS(status));
> +                       } else if (t->passed < 0) {
> +                               fprintf(TH_LOG_STREAM,
> +                                       "%s: Failed at step #%d\n",
> +                                       t->name,
> +                                       t->passed * -1);
> +                               t->passed = 0;
>                         }

Instead of creating an overloaded mechanism here, perhaps have an
option reporting mechanism that can be enabled. Like adding to
__test_metadata "bool no_stream; int test_number;" and adding
test_number++ to each ASSERT/EXCEPT call, and doing something like:

if (t->no_stream) {
                              fprintf(TH_LOG_STREAM,
                                      "%s: Failed at step #%d\n",
                                      t->name,
                                       t->test_number);
}

It'd be a cleaner approach, maybe?

-Kees

-- 
Kees Cook
Pixel Security