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 <mic@xxxxxxxxxxxxxxxxxxx> >>>> >>>> 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@xxxxxxxxx> >>>> Cc: Jann Horn <jannh@xxxxxxxxxx> >>>> Cc: Kees Cook <keescook@xxxxxxxxxxxx> >>>> Cc: Serge E. Hallyn <serge@xxxxxxxxxx> >>>> Cc: Shuah Khan <shuah@xxxxxxxxxx> >>>> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> >>>> Reviewed-by: Vincent Dagonneau <vincent.dagonneau@xxxxxxxxxxx> >>>> Link: https://lore.kernel.org/r/20210316204252.427806-11-mic@xxxxxxxxxxx >>> >>> 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. :)
