From: Kees Cook <keescook@chromium.org>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: "James Morris" <jmorris@namei.org>,
"Jann Horn" <jannh@google.com>,
"Serge E . Hallyn" <serge@hallyn.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Andy Lutomirski" <luto@amacapital.net>,
"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"David Howells" <dhowells@redhat.com>,
"Jeff Dike" <jdike@addtoit.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
"Richard Weinberger" <richard@nod.at>,
"Shuah Khan" <shuah@kernel.org>,
"Vincent Dagonneau" <vincent.dagonneau@ssi.gouv.fr>,
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,
"Mickaël Salaün" <mic@linux.microsoft.com>,
"Dmitry Vyukov" <dvyukov@google.com>
Subject: Re: [PATCH v30 10/12] selftests/landlock: Add user space tests
Date: Fri, 19 Mar 2021 12:11:39 -0700 [thread overview]
Message-ID: <202103191207.E12FD4E51@keescook> (raw)
In-Reply-To: <e98a1f48-4c35-139d-af88-b6e65fbb5c3f@digikod.net>
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 <mic@linux.microsoft.com>
> >>
> >> 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 <jmorris@namei.org>
> >> Cc: Jann Horn <jannh@google.com>
> >> Cc: Kees Cook <keescook@chromium.org>
> >> Cc: Serge E. Hallyn <serge@hallyn.com>
> >> Cc: Shuah Khan <shuah@kernel.org>
> >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
> >> Reviewed-by: Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>
> >> 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?
> >
> >> +/*
> >> + * 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.
--
Kees Cook
next prev parent reply other threads:[~2021-03-19 19:12 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 20:42 [PATCH v30 00/12] Landlock LSM Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 01/12] landlock: Add object management Mickaël Salaün
2021-03-19 18:13 ` Kees Cook
2021-03-19 18:57 ` Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2021-03-19 18:40 ` Kees Cook
2021-03-19 19:03 ` Mickaël Salaün
2021-03-19 19:15 ` Kees Cook
2021-03-24 20:31 ` James Morris
2021-03-25 9:29 ` Mickaël Salaün
2021-03-23 0:13 ` Jann Horn
2021-03-16 20:42 ` [PATCH v30 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2021-03-19 18:45 ` Kees Cook
2021-03-19 19:07 ` Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2021-03-19 18:45 ` Kees Cook
2021-03-16 20:42 ` [PATCH v30 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2021-03-19 17:24 ` Kees Cook
2021-03-16 20:42 ` [PATCH v30 06/12] fs,security: Add sb_delete hook Mickaël Salaün
2021-03-19 17:24 ` Kees Cook
2021-03-16 20:42 ` [PATCH v30 07/12] landlock: Support filesystem access-control Mickaël Salaün
2021-03-18 23:10 ` James Morris
2021-03-19 18:57 ` Kees Cook
2021-03-19 19:19 ` Mickaël Salaün
2021-03-23 19:30 ` Mickaël Salaün
2021-03-23 0:13 ` Jann Horn
2021-03-23 15:55 ` Mickaël Salaün
2021-03-23 17:49 ` Jann Horn
2021-03-23 19:22 ` Mickaël Salaün
2021-03-24 3:10 ` Jann Horn
2021-03-16 20:42 ` [PATCH v30 08/12] landlock: Add syscall implementations Mickaël Salaün
2021-03-19 19:06 ` Kees Cook
2021-03-19 21:53 ` Mickaël Salaün
2021-03-24 15:03 ` Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 09/12] arch: Wire up Landlock syscalls Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 10/12] selftests/landlock: Add user space tests Mickaël Salaün
2021-03-19 17:56 ` Kees Cook
2021-03-19 18:41 ` Mickaël Salaün
2021-03-19 19:11 ` Kees Cook [this message]
2021-03-19 21:57 ` Mickaël Salaün
2021-03-16 20:42 ` [PATCH v30 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2021-03-19 17:26 ` Kees Cook
2021-03-16 20:42 ` [PATCH v30 12/12] landlock: Add user and kernel documentation Mickaël Salaün
2021-03-19 18:03 ` Kees Cook
2021-03-19 18:54 ` Mickaël Salaün
2021-03-23 19:25 ` Mickaël Salaün
2021-03-24 16:21 ` Mickaël Salaün
2021-03-18 23:26 ` [PATCH v30 00/12] Landlock LSM James Morris
2021-03-19 15:52 ` Mickaël Salaün
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