From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 216CBC433E1 for ; Fri, 19 Mar 2021 21:58:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8B9961986 for ; Fri, 19 Mar 2021 21:58:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230177AbhCSV5u (ORCPT ); Fri, 19 Mar 2021 17:57:50 -0400 Received: from smtp-8fae.mail.infomaniak.ch ([83.166.143.174]:41153 "EHLO smtp-8fae.mail.infomaniak.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229974AbhCSV5q (ORCPT ); Fri, 19 Mar 2021 17:57:46 -0400 Received: from smtp-3-0000.mail.infomaniak.ch (unknown [10.4.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4F2HnP27SzzMq6wY; Fri, 19 Mar 2021 22:57:45 +0100 (CET) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4F2HnM4X8tzlh8T5; Fri, 19 Mar 2021 22:57:43 +0100 (CET) Subject: Re: [PATCH v30 10/12] selftests/landlock: Add user space tests To: Kees Cook Cc: James Morris , Jann Horn , "Serge E . Hallyn" , Al Viro , Andrew Morton , Andy Lutomirski , Anton Ivanov , Arnd Bergmann , Casey Schaufler , David Howells , Jeff Dike , Jonathan Corbet , Michael Kerrisk , Richard Weinberger , Shuah Khan , Vincent Dagonneau , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-security-module@vger.kernel.org, x86@kernel.org, =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= , Dmitry Vyukov References: <20210316204252.427806-1-mic@digikod.net> <20210316204252.427806-11-mic@digikod.net> <202103191026.D936362B@keescook> <202103191207.E12FD4E51@keescook> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= Message-ID: <1b043379-b6eb-d272-c9b9-25c6960e1ef1@digikod.net> Date: Fri, 19 Mar 2021 22:57:59 +0100 User-Agent: MIME-Version: 1.0 In-Reply-To: <202103191207.E12FD4E51@keescook> Content-Type: text/plain; charset=iso-8859-15 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: On 19/03/2021 20:11, Kees Cook wrote: > On Fri, Mar 19, 2021 at 07:41:00PM +0100, Mickaël Salaün wrote: >> >> On 19/03/2021 18:56, Kees Cook wrote: >>> On Tue, Mar 16, 2021 at 09:42:50PM +0100, Mickaël Salaün wrote: >>>> From: Mickaël Salaün >>>> >>>> Test all Landlock system calls, ptrace hooks semantic and filesystem >>>> access-control with multiple layouts. >>>> >>>> Test coverage for security/landlock/ is 93.6% of lines. The code not >>>> covered only deals with internal kernel errors (e.g. memory allocation) >>>> and race conditions. >>>> >>>> Cc: James Morris >>>> Cc: Jann Horn >>>> Cc: Kees Cook >>>> Cc: Serge E. Hallyn >>>> Cc: Shuah Khan >>>> Signed-off-by: Mickaël Salaün >>>> Reviewed-by: Vincent Dagonneau >>>> Link: https://lore.kernel.org/r/20210316204252.427806-11-mic@digikod.net >>> >>> This is terrific. I love the coverage. How did you measure this, BTW? >> >> I used gcov: https://www.kernel.org/doc/html/latest/dev-tools/gcov.html >> >>> To increase it into memory allocation failures, have you tried >>> allocation fault injection: >>> https://www.kernel.org/doc/html/latest/fault-injection/fault-injection.html >> >> Yes, it is used by syzkaller, but I don't know how to extract this >> specific coverage. >> >>> >>>> [...] >>>> +TEST(inconsistent_attr) { >>>> + const long page_size = sysconf(_SC_PAGESIZE); >>>> + char *const buf = malloc(page_size + 1); >>>> + struct landlock_ruleset_attr *const ruleset_attr = (void *)buf; >>>> + >>>> + ASSERT_NE(NULL, buf); >>>> + >>>> + /* Checks copy_from_user(). */ >>>> + ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, 0, 0)); >>>> + /* The size if less than sizeof(struct landlock_attr_enforce). */ >>>> + ASSERT_EQ(EINVAL, errno); >>>> + ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, 1, 0)); >>>> + ASSERT_EQ(EINVAL, errno); >>> >>> Almost everywhere you're using ASSERT instead of EXPECT. Is this correct >>> (in the sense than as soon as an ASSERT fails the rest of the test is >>> skipped)? I do see you using EXPECT is some places, but I figured I'd >>> ask about the intention here. >> >> I intentionally use ASSERT as much as possible, but I use EXPECT when an >> error could block a test or when it could stop a cleanup (i.e. teardown). > > Okay. Does the test suite run sanely when landlock is missing from the > kernel? When Landlock is disabled, the tests fail but do not hang. > >>> >>>> +/* >>>> + * TEST_F_FORK() is useful when a test drop privileges but the corresponding >>>> + * FIXTURE_TEARDOWN() requires them (e.g. to remove files from a directory >>>> + * where write actions are denied). For convenience, FIXTURE_TEARDOWN() is >>>> + * also called when the test failed, but not when FIXTURE_SETUP() failed. For >>>> + * this to be possible, we must not call abort() but instead exit smoothly >>>> + * (hence the step print). >>>> + */ >>> >>> Hm, interesting. I think this should be extracted into a separate patch >>> and added to the test harness proper. >> >> I agree, but it may require some modifications to fit nicely in >> kselftest_harness.h . For now, it works well for my use case. I'll send >> patches once Landlock is merged. In fact, I already made >> kselftest_harness.h available for other users than seccomp. ;) > > Fair points. > >>> >>> Could this be solved with TEARDOWN being called on SETUP failure? >> >> The goal of this helper is to still be able to call TEARDOWN when TEST >> failed, not SETUP. >> >>> >>>> +#define TEST_F_FORK(fixture_name, test_name) \ >>>> + static void fixture_name##_##test_name##_child( \ >>>> + struct __test_metadata *_metadata, \ >>>> + FIXTURE_DATA(fixture_name) *self, \ >>>> + const FIXTURE_VARIANT(fixture_name) *variant); \ >>>> + TEST_F(fixture_name, test_name) \ >>>> + { \ >>>> + int status; \ >>>> + const pid_t child = fork(); \ >>>> + if (child < 0) \ >>>> + abort(); \ >>>> + if (child == 0) { \ >>>> + _metadata->no_print = 1; \ >>>> + fixture_name##_##test_name##_child(_metadata, self, variant); \ >>>> + if (_metadata->skip) \ >>>> + _exit(255); \ >>>> + if (_metadata->passed) \ >>>> + _exit(0); \ >>>> + _exit(_metadata->step); \ >>>> + } \ >>>> + if (child != waitpid(child, &status, 0)) \ >>>> + abort(); \ >>>> + if (WIFSIGNALED(status) || !WIFEXITED(status)) { \ >>>> + _metadata->passed = 0; \ >>>> + _metadata->step = 1; \ >>>> + return; \ >>>> + } \ >>>> + switch (WEXITSTATUS(status)) { \ >>>> + case 0: \ >>>> + _metadata->passed = 1; \ >>>> + break; \ >>>> + case 255: \ >>>> + _metadata->passed = 1; \ >>>> + _metadata->skip = 1; \ >>>> + break; \ >>>> + default: \ >>>> + _metadata->passed = 0; \ >>>> + _metadata->step = WEXITSTATUS(status); \ >>>> + break; \ >>>> + } \ >>>> + } \ >>> >>> This looks like a subset of __wait_for_test()? Could __TEST_F_IMPL() be >>> updated instead to do this? (Though the fork overhead might not be great >>> for everyone.) >> >> Yes, it will probably be my approach to update kselftest_harness.h . > > It seems like this would be named better as TEST_DROPS_PRIVS or something, > which describes the reason for the fork. Yeah, maybe, we could discuss about that in a dedicated patch series. :)