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? > > > >> +/* > >> + * 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
