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Date: Wed, 19 Apr 2017 15:02:34 -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 Wed, Apr 19, 2017 at 2:51 PM, Mickaël Salaün <mic@...ikod.net> wrote:
>
> On 19/04/2017 02:02, Kees Cook wrote:
>> 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?
>
> Because the return code of a process is capped to 8 bits and I use a
> negative value to not mess with the current interpretation of 0 (error)
> and 1 (OK) for the "passed" variable.
>
>>
>>>         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?
>
> Good idea, we will then be able to use 255 steps!
>
> Do you want me to send this as a separate patch?
>
> Can we move test_harness.h outside of the seccomp directory to be
> available to other subsystems as well?

Yeah, I would do two patches, and send them out separately (to shuah
with lkml and me in cc at least), one to move test_hardness.h into
some include/ directory, and then to add the new logic for streamless
reporting.

Thanks!

-Kees


-- 
Kees Cook
Pixel Security

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