Commit f55aef7e authored by Kees Cook's avatar Kees Cook
Browse files

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

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: default avatarKees Cook <kees@kernel.org>
parent b370f7ea

lib/tests/randstruct_kunit.c

+65 −14
Original line number Diff line number Diff line
@@ -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),

	{}

};