kunit/overflow: Fix DEFINE_FLEX tests for counted_by

Unfortunately, __builtin_dynamic_object_size() does not take into account
flexible array sizes, even when they are sized by __counted_by. As a
result, the size tests for the flexible arrays need to be separated to
get an accurate check of the compiler's behavior. While at it, fully test
sizeof, __struct_size (bdos(..., 0)), and __member_size (bdos(..., 1)).

I still think this is a compiler design issue, but there's not much to
be done about it currently beyond adjusting these tests. GCC and Clang
agree on this behavior at least. :)

Reported-by: "Thomas Weißschuh" <linux@weissschuh.net>
Closes: https://lore.kernel.org/lkml/e1a1531d-6968-4ae8-a3b5-5ea0547ec4b3@t-8ch.de/
Fixes: 9dd5134c6158 ("kunit/overflow: Adjust for __counted_by with DEFINE_RAW_FLEX()")
Signed-off-by: Kees Cook <kees@kernel.org>

diff --git a/lib/tests/overflow_kunit.c b/lib/tests/overflow_kunit.c
index 5222c6393f116865e3e3eab7ae22f1fc9ac787cb..894691b4411a34a24544ae52c7ad4935fec52802 100644 (file)
--- a/lib/tests/overflow_kunit.c
+++ b/lib/tests/overflow_kunit.c
@@ -1185,22 +1185,40 @@ struct bar {
 
 static void DEFINE_FLEX_test(struct kunit *test)
 {
-       /* Using _RAW_ on a __counted_by struct will initialize "counter" to zero */
-       DEFINE_RAW_FLEX(struct foo, two_but_zero, array, 2);
-#ifdef CONFIG_CC_HAS_COUNTED_BY
-       int expected_raw_size = sizeof(struct foo);
-#else
-       int expected_raw_size = sizeof(struct foo) + 2 * sizeof(s16);
-#endif
-       /* Without annotation, it will always be on-stack size. */
        DEFINE_RAW_FLEX(struct bar, two, array, 2);
        DEFINE_FLEX(struct foo, eight, array, counter, 8);
        DEFINE_FLEX(struct foo, empty, array, counter, 0);
+       /* Using _RAW_ on a __counted_by struct will initialize "counter" to zero */
+       DEFINE_RAW_FLEX(struct foo, two_but_zero, array, 2);
+       int array_size_override = 0;
 
-       KUNIT_EXPECT_EQ(test, __struct_size(two_but_zero), expected_raw_size);
+       KUNIT_EXPECT_EQ(test, sizeof(*two), sizeof(struct bar));
        KUNIT_EXPECT_EQ(test, __struct_size(two), sizeof(struct bar) + 2 * sizeof(s16));
-       KUNIT_EXPECT_EQ(test, __struct_size(eight), 24);
+       KUNIT_EXPECT_EQ(test, __member_size(two), sizeof(struct bar) + 2 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __struct_size(two->array), 2 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __member_size(two->array), 2 * sizeof(s16));
+
+       KUNIT_EXPECT_EQ(test, sizeof(*eight), sizeof(struct foo));
+       KUNIT_EXPECT_EQ(test, __struct_size(eight), sizeof(struct foo) + 8 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __member_size(eight), sizeof(struct foo) + 8 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __struct_size(eight->array), 8 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __member_size(eight->array), 8 * sizeof(s16));
+
+       KUNIT_EXPECT_EQ(test, sizeof(*empty), sizeof(struct foo));
        KUNIT_EXPECT_EQ(test, __struct_size(empty), sizeof(struct foo));
+       KUNIT_EXPECT_EQ(test, __member_size(empty), sizeof(struct foo));
+       KUNIT_EXPECT_EQ(test, __struct_size(empty->array), 0);
+       KUNIT_EXPECT_EQ(test, __member_size(empty->array), 0);
+
+       /* If __counted_by is not being used, array size will have the on-stack size. */
+       if (!IS_ENABLED(CONFIG_CC_HAS_COUNTED_BY))
+               array_size_override = 2 * sizeof(s16);
+
+       KUNIT_EXPECT_EQ(test, sizeof(*two_but_zero), sizeof(struct foo));
+       KUNIT_EXPECT_EQ(test, __struct_size(two_but_zero), sizeof(struct foo) + 2 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __member_size(two_but_zero), sizeof(struct foo) + 2 * sizeof(s16));
+       KUNIT_EXPECT_EQ(test, __struct_size(two_but_zero->array), array_size_override);
+       KUNIT_EXPECT_EQ(test, __member_size(two_but_zero->array), array_size_override);
 }
 
 static struct kunit_case overflow_test_cases[] = {