lib/tests: Add randstruct KUnit test

Perform basic validation about layout randomization and initialization
tracking when using CONFIG_RANDSTRUCT=y. Tested using:

$ ./tools/testing/kunit/kunit.py run \
	--kconfig_add CONFIG_RANDSTRUCT_FULL=y \
	randstruct
[17:22:30] ================= randstruct (2 subtests) ==================
[17:22:30] [PASSED] randstruct_layout
[17:22:30] [PASSED] randstruct_initializers
[17:22:30] =================== [PASSED] randstruct ====================
[17:22:30] ============================================================
[17:22:30] Testing complete. Ran 2 tests: passed: 2
[17:22:30] Elapsed time: 5.091s total, 0.001s configuring, 4.974s building, 0.086s running

Adding "--make_option LLVM=1" can be used to test Clang, which also
passes.

Acked-by: David Gow <davidgow@google.com>
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Kees Cook 2025-04-26 17:21:01 -07:00
parent e136a40621
commit b370f7eacd
4 changed files with 293 additions and 0 deletions

View File

@ -12892,6 +12892,7 @@ F: include/linux/overflow.h
F: include/linux/randomize_kstack.h
F: include/linux/ucopysize.h
F: kernel/configs/hardening.config
F: lib/tests/randstruct_kunit.c
F: lib/tests/usercopy_kunit.c
F: mm/usercopy.c
F: security/Kconfig.hardening

View File

@ -2863,6 +2863,14 @@ config OVERFLOW_KUNIT_TEST
If unsure, say N.
config RANDSTRUCT_KUNIT_TEST
tristate "Test randstruct structure layout randomization at runtime" if !KUNIT_ALL_TESTS
depends on KUNIT
default KUNIT_ALL_TESTS
help
Builds unit tests for the checking CONFIG_RANDSTRUCT=y, which
randomizes structure layouts.
config STACKINIT_KUNIT_TEST
tristate "Test level of stack variable initialization" if !KUNIT_ALL_TESTS
depends on KUNIT

View File

@ -35,6 +35,7 @@ obj-$(CONFIG_MEMCPY_KUNIT_TEST) += memcpy_kunit.o
CFLAGS_overflow_kunit.o = $(call cc-disable-warning, tautological-constant-out-of-range-compare)
obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o
obj-$(CONFIG_PRINTF_KUNIT_TEST) += printf_kunit.o
obj-$(CONFIG_RANDSTRUCT_KUNIT_TEST) += randstruct_kunit.o
obj-$(CONFIG_SCANF_KUNIT_TEST) += scanf_kunit.o
obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o
obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o

View File

@ -0,0 +1,283 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Test cases for struct randomization, i.e. CONFIG_RANDSTRUCT=y.
*
* For example, see:
* "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst
* ./tools/testing/kunit/kunit.py run randstruct [--raw_output] \
* [--make_option LLVM=1] \
* --kconfig_add CONFIG_RANDSTRUCT_FULL=y
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <kunit/test.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/string.h>
#define DO_MANY_MEMBERS(macro, args...) \
macro(a, args) \
macro(b, args) \
macro(c, args) \
macro(d, args) \
macro(e, args) \
macro(f, args) \
macro(g, args) \
macro(h, args)
#define do_enum(x, ignored) MEMBER_NAME_ ## x,
enum randstruct_member_names {
DO_MANY_MEMBERS(do_enum)
MEMBER_NAME_MAX,
};
/* Make sure the macros are working: want 8 test members. */
_Static_assert(MEMBER_NAME_MAX == 8, "Number of test members changed?!");
/* This is an unsigned long member to match the function pointer size */
#define unsigned_long_member(x, ignored) unsigned long x;
struct randstruct_untouched {
DO_MANY_MEMBERS(unsigned_long_member)
};
/* Struct explicitly marked with __randomize_layout. */
struct randstruct_shuffled {
DO_MANY_MEMBERS(unsigned_long_member)
} __randomize_layout;
#undef unsigned_long_member
/* Struct implicitly randomized from being all func ptrs. */
#define func_member(x, ignored) size_t (*x)(int);
struct randstruct_funcs_untouched {
DO_MANY_MEMBERS(func_member)
} __no_randomize_layout;
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) \
{ \
return offsetof(struct randstruct_funcs_untouched, x); \
}
DO_MANY_MEMBERS(func_body)
/* Various mixed types. */
#define mixed_members \
bool a; \
short b; \
unsigned int c __aligned(16); \
size_t d; \
char e; \
u64 f; \
union { \
struct randstruct_shuffled shuffled; \
uintptr_t g; \
}; \
union { \
void *ptr; \
char h; \
};
struct randstruct_mixed_untouched {
mixed_members
};
struct randstruct_mixed_shuffled {
mixed_members
} __randomize_layout;
#undef mixed_members
struct contains_randstruct_untouched {
int before;
struct randstruct_untouched untouched;
int after;
};
struct contains_randstruct_shuffled {
int before;
struct randstruct_shuffled shuffled;
int after;
};
static void randstruct_layout(struct kunit *test)
{
int mismatches;
#define check_mismatch(x, untouched, shuffled) \
if (offsetof(untouched, x) != offsetof(shuffled, x)) \
mismatches++; \
kunit_info(test, #shuffled "::" #x " @ %zu (vs %zu)\n", \
offsetof(shuffled, x), \
offsetof(untouched, x)); \
#define check_pair(outcome, untouched, shuffled) \
mismatches = 0; \
DO_MANY_MEMBERS(check_mismatch, 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
#undef check_mismatch
}
#define check_mismatch(x, ignore) \
KUNIT_EXPECT_EQ_MSG(test, untouched->x, shuffled->x, \
"Mismatched member value in %s initializer\n", \
name);
static void test_check_init(struct kunit *test, const char *name,
struct randstruct_untouched *untouched,
struct randstruct_shuffled *shuffled)
{
DO_MANY_MEMBERS(check_mismatch)
}
static void test_check_mixed_init(struct kunit *test, const char *name,
struct randstruct_mixed_untouched *untouched,
struct randstruct_mixed_shuffled *shuffled)
{
DO_MANY_MEMBERS(check_mismatch)
}
#undef check_mismatch
#define check_mismatch(x, ignore) \
KUNIT_EXPECT_EQ_MSG(test, untouched->untouched.x, \
shuffled->shuffled.x, \
"Mismatched member value in %s initializer\n", \
name);
static void test_check_contained_init(struct kunit *test, const char *name,
struct contains_randstruct_untouched *untouched,
struct contains_randstruct_shuffled *shuffled)
{
DO_MANY_MEMBERS(check_mismatch)
}
#undef check_mismatch
#define check_mismatch(x, ignore) \
KUNIT_EXPECT_PTR_EQ_MSG(test, untouched->x, shuffled->x, \
"Mismatched member value in %s initializer\n", \
name);
static void test_check_funcs_init(struct kunit *test, const char *name,
struct randstruct_funcs_untouched *untouched,
struct randstruct_funcs_shuffled *shuffled)
{
DO_MANY_MEMBERS(check_mismatch)
}
#undef check_mismatch
static void randstruct_initializers(struct kunit *test)
{
#define init_members \
.a = 1, \
.b = 3, \
.c = 5, \
.d = 7, \
.e = 11, \
.f = 13, \
.g = 17, \
.h = 19,
struct randstruct_untouched untouched = {
init_members
};
struct randstruct_shuffled shuffled = {
init_members
};
struct randstruct_mixed_untouched mixed_untouched = {
init_members
};
struct randstruct_mixed_shuffled mixed_shuffled = {
init_members
};
struct contains_randstruct_untouched contains_untouched = {
.untouched = {
init_members
},
};
struct contains_randstruct_shuffled contains_shuffled = {
.shuffled = {
init_members
},
};
#define func_member(x, ignored) \
.x = func_##x,
struct randstruct_funcs_untouched funcs_untouched = {
DO_MANY_MEMBERS(func_member)
};
struct randstruct_funcs_shuffled funcs_shuffled = {
DO_MANY_MEMBERS(func_member)
};
test_check_init(test, "named", &untouched, &shuffled);
test_check_init(test, "unnamed", &untouched,
&(struct randstruct_shuffled){
init_members
});
test_check_contained_init(test, "named", &contains_untouched, &contains_shuffled);
test_check_contained_init(test, "unnamed", &contains_untouched,
&(struct contains_randstruct_shuffled){
.shuffled = (struct randstruct_shuffled){
init_members
},
});
test_check_contained_init(test, "named", &contains_untouched, &contains_shuffled);
test_check_contained_init(test, "unnamed copy", &contains_untouched,
&(struct contains_randstruct_shuffled){
/* full struct copy initializer */
.shuffled = shuffled,
});
test_check_mixed_init(test, "named", &mixed_untouched, &mixed_shuffled);
test_check_mixed_init(test, "unnamed", &mixed_untouched,
&(struct randstruct_mixed_shuffled){
init_members
});
test_check_funcs_init(test, "named", &funcs_untouched, &funcs_shuffled);
test_check_funcs_init(test, "unnamed", &funcs_untouched,
&(struct randstruct_funcs_shuffled){
DO_MANY_MEMBERS(func_member)
});
#undef func_member
#undef init_members
}
static int randstruct_test_init(struct kunit *test)
{
if (!IS_ENABLED(CONFIG_RANDSTRUCT))
kunit_skip(test, "Not built with CONFIG_RANDSTRUCT=y");
return 0;
}
static struct kunit_case randstruct_test_cases[] = {
KUNIT_CASE(randstruct_layout),
KUNIT_CASE(randstruct_initializers),
{}
};
static struct kunit_suite randstruct_test_suite = {
.name = "randstruct",
.init = randstruct_test_init,
.test_cases = randstruct_test_cases,
};
kunit_test_suites(&randstruct_test_suite);
MODULE_DESCRIPTION("Test cases for struct randomization");
MODULE_LICENSE("GPL");