selftests/landlock: Extend tests for minimal valid attribute size

This might be useful when the struct landlock_ruleset_attr will get more
fields.

Cc: Shuah Khan <shuah@kernel.org>
Link: https://lore.kernel.org/r/20220506160820.524344-4-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

tools/testing/selftests/landlock/base_test.c

@@ -35,6 +35,8 @@ TEST(inconsistent_attr)
 	ASSERT_EQ(EINVAL, errno);
 	ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, 1, 0));
 	ASSERT_EQ(EINVAL, errno);
+	ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, 7, 0));
+	ASSERT_EQ(EINVAL, errno);
 
 	ASSERT_EQ(-1, landlock_create_ruleset(NULL, 1, 0));
 	/* The size if less than sizeof(struct landlock_attr_enforce). */
@@ -47,6 +49,9 @@ TEST(inconsistent_attr)
 	ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, page_size + 1, 0));
 	ASSERT_EQ(E2BIG, errno);
 
+	/* Checks minimal valid attribute size. */
+	ASSERT_EQ(-1, landlock_create_ruleset(ruleset_attr, 8, 0));
+	ASSERT_EQ(ENOMSG, errno);
 	ASSERT_EQ(-1, landlock_create_ruleset(
 			      ruleset_attr,
 			      sizeof(struct landlock_ruleset_attr), 0));