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).
+/*
- 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. ;)
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 .