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lib/tests: randstruct: Add deep function pointer layout test

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The recent fix in commit c2ea09b193d2 ("randstruct: gcc-plugin: Remove
bogus void member") has fixed another issue: it was not always detecting
composite structures made only of function pointers and structures of
function pointers. Add a test for this case, and break out the layout
tests since this issue is actually a problem for Clang as well[1].

Link: https://github.com/llvm/llvm-project/issues/138355 [1]
Link: https://lore.kernel.org/r/20250502224116.work.591-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Kees Cook 2025-05-02 15:41:20 -07:00
parent b370f7eacd
commit f55aef7e0c
1 changed files with 65 additions and 14 deletions
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79
lib/tests/randstruct_kunit.c
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@ -56,7 +56,6 @@ struct randstruct_funcs_untouched {
struct randstruct_funcs_shuffled {
DO_MANY_MEMBERS(func_member)
};
#undef func_member
#define func_body(x, ignored) \
static noinline size_t func_##x(int arg) \
@ -103,9 +102,16 @@ struct contains_randstruct_shuffled {
int after;
};
static void randstruct_layout(struct kunit *test)
{
int mismatches;
struct contains_func_untouched {
struct randstruct_funcs_shuffled inner;
DO_MANY_MEMBERS(func_member)
} __no_randomize_layout;
struct contains_func_shuffled {
struct randstruct_funcs_shuffled inner;
DO_MANY_MEMBERS(func_member)
};
#undef func_member
#define check_mismatch(x, untouched, shuffled) \
if (offsetof(untouched, x) != offsetof(shuffled, x)) \
@ -114,24 +120,66 @@ static void randstruct_layout(struct kunit *test)
offsetof(shuffled, x), \
offsetof(untouched, x)); \
#define check_pair(outcome, untouched, shuffled) \
#define check_pair(outcome, untouched, shuffled, checker...) \
mismatches = 0; \
DO_MANY_MEMBERS(check_mismatch, untouched, shuffled) \
DO_MANY_MEMBERS(checker, untouched, shuffled) \
kunit_info(test, "Differing " #untouched " vs " #shuffled " member positions: %d\n", \
mismatches); \
KUNIT_##outcome##_MSG(test, mismatches, 0, \
#untouched " vs " #shuffled " layouts: unlucky or broken?\n");
check_pair(EXPECT_EQ, struct randstruct_untouched, struct randstruct_untouched)
check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_shuffled)
check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_funcs_shuffled)
check_pair(EXPECT_GT, struct randstruct_funcs_untouched, struct randstruct_funcs_shuffled)
check_pair(EXPECT_GT, struct randstruct_mixed_untouched, struct randstruct_mixed_shuffled)
#undef check_pair
static void randstruct_layout_same(struct kunit *test)
{
int mismatches;
#undef check_mismatch
check_pair(EXPECT_EQ, struct randstruct_untouched, struct randstruct_untouched,
check_mismatch)
check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_shuffled,
check_mismatch)
}
static void randstruct_layout_mixed(struct kunit *test)
{
int mismatches;
check_pair(EXPECT_EQ, struct randstruct_mixed_untouched, struct randstruct_mixed_untouched,
check_mismatch)
check_pair(EXPECT_GT, struct randstruct_mixed_untouched, struct randstruct_mixed_shuffled,
check_mismatch)
}
static void randstruct_layout_fptr(struct kunit *test)
{
int mismatches;
check_pair(EXPECT_EQ, struct randstruct_untouched, struct randstruct_untouched,
check_mismatch)
check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_funcs_shuffled,
check_mismatch)
check_pair(EXPECT_GT, struct randstruct_funcs_untouched, struct randstruct_funcs_shuffled,
check_mismatch)
}
#define check_mismatch_prefixed(x, prefix, untouched, shuffled) \
check_mismatch(prefix.x, untouched, shuffled)
static void randstruct_layout_fptr_deep(struct kunit *test)
{
int mismatches;
if (IS_ENABLED(CONFIG_CC_IS_CLANG))
kunit_skip(test, "Clang randstruct misses inner functions: https://github.com/llvm/llvm-project/issues/138355");
check_pair(EXPECT_EQ, struct contains_func_untouched, struct contains_func_untouched,
check_mismatch_prefixed, inner)
check_pair(EXPECT_GT, struct contains_func_untouched, struct contains_func_shuffled,
check_mismatch_prefixed, inner)
}
#undef check_pair
#undef check_mismatch
#define check_mismatch(x, ignore) \
KUNIT_EXPECT_EQ_MSG(test, untouched->x, shuffled->x, \
"Mismatched member value in %s initializer\n", \
@ -266,7 +314,10 @@ static int randstruct_test_init(struct kunit *test)
}
static struct kunit_case randstruct_test_cases[] = {
KUNIT_CASE(randstruct_layout),
KUNIT_CASE(randstruct_layout_same),
KUNIT_CASE(randstruct_layout_mixed),
KUNIT_CASE(randstruct_layout_fptr),
KUNIT_CASE(randstruct_layout_fptr_deep),
KUNIT_CASE(randstruct_initializers),
{}
};