1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Test cases for compiler-based stack variable zeroing via 4 * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*. 5 * For example, see: 6 * "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst 7 * ./tools/testing/kunit/kunit.py run stackinit [--raw_output] \ 8 * --make_option LLVM=1 \ 9 * --kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y 10 * 11 */ 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 13 14 #include <kunit/test.h> 15 #include <linux/init.h> 16 #include <linux/kernel.h> 17 #include <linux/module.h> 18 #include <linux/string.h> 19 20 /* Exfiltration buffer. */ 21 #define MAX_VAR_SIZE 128 22 static u8 check_buf[MAX_VAR_SIZE]; 23 24 /* Character array to trigger stack protector in all functions. */ 25 #define VAR_BUFFER 32 26 27 /* Volatile mask to convince compiler to copy memory with 0xff. */ 28 static volatile u8 forced_mask = 0xff; 29 30 /* Location and size tracking to validate fill and test are colocated. */ 31 static void *fill_start, *target_start; 32 static size_t fill_size, target_size; 33 34 static bool stackinit_range_contains(char *haystack_start, size_t haystack_size, 35 char *needle_start, size_t needle_size) 36 { 37 if (needle_start >= haystack_start && 38 needle_start + needle_size <= haystack_start + haystack_size) 39 return true; 40 return false; 41 } 42 43 /* Whether the test is expected to fail. */ 44 #define WANT_SUCCESS 0 45 #define XFAIL 1 46 47 #define DO_NOTHING_TYPE_SCALAR(var_type) var_type 48 #define DO_NOTHING_TYPE_STRING(var_type) void 49 #define DO_NOTHING_TYPE_STRUCT(var_type) void 50 51 #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr) 52 #define DO_NOTHING_RETURN_STRING(ptr) /**/ 53 #define DO_NOTHING_RETURN_STRUCT(ptr) /**/ 54 55 #define DO_NOTHING_CALL_SCALAR(var, name) \ 56 (var) = do_nothing_ ## name(&(var)) 57 #define DO_NOTHING_CALL_STRING(var, name) \ 58 do_nothing_ ## name(var) 59 #define DO_NOTHING_CALL_STRUCT(var, name) \ 60 do_nothing_ ## name(&(var)) 61 62 #define FETCH_ARG_SCALAR(var) &var 63 #define FETCH_ARG_STRING(var) var 64 #define FETCH_ARG_STRUCT(var) &var 65 66 /* 67 * On m68k, if the leaf function test variable is longer than 8 bytes, 68 * the start of the stack frame moves. 8 is sufficiently large to 69 * test m68k char arrays, but leave it at 16 for other architectures. 70 */ 71 #ifdef CONFIG_M68K 72 #define FILL_SIZE_STRING 8 73 #else 74 #define FILL_SIZE_STRING 16 75 #endif 76 77 #define INIT_CLONE_SCALAR /**/ 78 #define INIT_CLONE_STRING [FILL_SIZE_STRING] 79 #define INIT_CLONE_STRUCT /**/ 80 81 #define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero)) 82 #define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero)) 83 /* 84 * For the struct, intentionally poison padding to see if it gets 85 * copied out in direct assignments. 86 * */ 87 #define ZERO_CLONE_STRUCT(zero) \ 88 do { \ 89 memset(&(zero), 0xFF, sizeof(zero)); \ 90 zero.one = 0; \ 91 zero.two = 0; \ 92 zero.three = 0; \ 93 zero.four = 0; \ 94 } while (0) 95 96 #define INIT_SCALAR_none(var_type) /**/ 97 #define INIT_SCALAR_zero(var_type) = 0 98 99 #define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/ 100 #define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { } 101 102 #define INIT_STRUCT_none(var_type) /**/ 103 #define INIT_STRUCT_zero(var_type) = { } 104 105 106 #define __static_partial { .two = 0, } 107 #define __static_all { .one = 0, \ 108 .two = 0, \ 109 .three = 0, \ 110 .four = 0, \ 111 } 112 #define __dynamic_partial { .two = arg->two, } 113 #define __dynamic_all { .one = arg->one, \ 114 .two = arg->two, \ 115 .three = arg->three, \ 116 .four = arg->four, \ 117 } 118 #define __runtime_partial var.two = 0 119 #define __runtime_all var.one = 0; \ 120 var.two = 0; \ 121 var.three = 0; \ 122 var.four = 0 123 124 #define INIT_STRUCT_static_partial(var_type) \ 125 = __static_partial 126 #define INIT_STRUCT_static_all(var_type) \ 127 = __static_all 128 #define INIT_STRUCT_dynamic_partial(var_type) \ 129 = __dynamic_partial 130 #define INIT_STRUCT_dynamic_all(var_type) \ 131 = __dynamic_all 132 #define INIT_STRUCT_runtime_partial(var_type) \ 133 ; __runtime_partial 134 #define INIT_STRUCT_runtime_all(var_type) \ 135 ; __runtime_all 136 137 #define INIT_STRUCT_assigned_static_partial(var_type) \ 138 ; var = (var_type)__static_partial 139 #define INIT_STRUCT_assigned_static_all(var_type) \ 140 ; var = (var_type)__static_all 141 #define INIT_STRUCT_assigned_dynamic_partial(var_type) \ 142 ; var = (var_type)__dynamic_partial 143 #define INIT_STRUCT_assigned_dynamic_all(var_type) \ 144 ; var = (var_type)__dynamic_all 145 146 #define INIT_STRUCT_assigned_copy(var_type) \ 147 ; var = *(arg) 148 149 /* 150 * @name: unique string name for the test 151 * @var_type: type to be tested for zeroing initialization 152 * @which: is this a SCALAR, STRING, or STRUCT type? 153 * @init_level: what kind of initialization is performed 154 * @xfail: is this test expected to fail? 155 */ 156 #define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \ 157 /* Returns 0 on success, 1 on failure. */ \ 158 static noinline void test_ ## name (struct kunit *test) \ 159 { \ 160 var_type zero INIT_CLONE_ ## which; \ 161 int ignored; \ 162 u8 sum = 0, i; \ 163 \ 164 /* Notice when a new test is larger than expected. */ \ 165 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \ 166 \ 167 /* Fill clone type with zero for per-field init. */ \ 168 ZERO_CLONE_ ## which(zero); \ 169 /* Clear entire check buffer for 0xFF overlap test. */ \ 170 memset(check_buf, 0x00, sizeof(check_buf)); \ 171 /* Fill stack with 0xFF. */ \ 172 ignored = leaf_ ##name((unsigned long)&ignored, 1, \ 173 FETCH_ARG_ ## which(zero)); \ 174 /* Verify all bytes overwritten with 0xFF. */ \ 175 for (sum = 0, i = 0; i < target_size; i++) \ 176 sum += (check_buf[i] != 0xFF); \ 177 /* Clear entire check buffer for later bit tests. */ \ 178 memset(check_buf, 0x00, sizeof(check_buf)); \ 179 /* Extract stack-defined variable contents. */ \ 180 ignored = leaf_ ##name((unsigned long)&ignored, 0, \ 181 FETCH_ARG_ ## which(zero)); \ 182 /* \ 183 * Delay the sum test to here to do as little as \ 184 * possible between the two leaf function calls. \ 185 */ \ 186 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \ 187 "leaf fill was not 0xFF!?\n"); \ 188 \ 189 /* Validate that compiler lined up fill and target. */ \ 190 KUNIT_ASSERT_TRUE_MSG(test, \ 191 stackinit_range_contains(fill_start, fill_size, \ 192 target_start, target_size), \ 193 "stackframe was not the same between calls!? " \ 194 "(fill %zu wide, target offset by %d)\n", \ 195 fill_size, \ 196 (int)((ssize_t)(uintptr_t)fill_start - \ 197 (ssize_t)(uintptr_t)target_start)); \ 198 \ 199 /* Look for any bytes still 0xFF in check region. */ \ 200 for (sum = 0, i = 0; i < target_size; i++) \ 201 sum += (check_buf[i] == 0xFF); \ 202 \ 203 if (sum != 0 && xfail) \ 204 kunit_skip(test, \ 205 "XFAIL uninit bytes: %d\n", \ 206 sum); \ 207 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \ 208 "uninit bytes: %d\n", sum); \ 209 } 210 #define DEFINE_TEST(name, var_type, which, init_level, xfail) \ 211 /* no-op to force compiler into ignoring "uninitialized" vars */\ 212 static noinline DO_NOTHING_TYPE_ ## which(var_type) \ 213 do_nothing_ ## name(var_type *ptr) \ 214 { \ 215 /* Will always be true, but compiler doesn't know. */ \ 216 if ((unsigned long)ptr > 0x2) \ 217 return DO_NOTHING_RETURN_ ## which(ptr); \ 218 else \ 219 return DO_NOTHING_RETURN_ ## which(ptr + 1); \ 220 } \ 221 static noinline int leaf_ ## name(unsigned long sp, bool fill, \ 222 var_type *arg) \ 223 { \ 224 char buf[VAR_BUFFER]; \ 225 var_type var \ 226 INIT_ ## which ## _ ## init_level(var_type); \ 227 \ 228 target_start = &var; \ 229 target_size = sizeof(var); \ 230 /* \ 231 * Keep this buffer around to make sure we've got a \ 232 * stack frame of SOME kind... \ 233 */ \ 234 memset(buf, (char)(sp & 0xff), sizeof(buf)); \ 235 /* Fill variable with 0xFF. */ \ 236 if (fill) { \ 237 fill_start = &var; \ 238 fill_size = sizeof(var); \ 239 memset(fill_start, \ 240 (char)((sp & 0xff) | forced_mask), \ 241 fill_size); \ 242 } \ 243 \ 244 /* Silence "never initialized" warnings. */ \ 245 DO_NOTHING_CALL_ ## which(var, name); \ 246 \ 247 /* Exfiltrate "var". */ \ 248 memcpy(check_buf, target_start, target_size); \ 249 \ 250 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \ 251 } \ 252 DEFINE_TEST_DRIVER(name, var_type, which, xfail) 253 254 /* Structure with no padding. */ 255 struct test_packed { 256 unsigned long one; 257 unsigned long two; 258 unsigned long three; 259 unsigned long four; 260 }; 261 262 /* Simple structure with padding likely to be covered by compiler. */ 263 struct test_small_hole { 264 size_t one; 265 char two; 266 /* 3 byte padding hole here. */ 267 int three; 268 unsigned long four; 269 }; 270 271 /* Trigger unhandled padding in a structure. */ 272 struct test_big_hole { 273 u8 one; 274 u8 two; 275 u8 three; 276 /* 61 byte padding hole here. */ 277 u8 four __aligned(64); 278 } __aligned(64); 279 280 struct test_trailing_hole { 281 char *one; 282 char *two; 283 char *three; 284 char four; 285 /* "sizeof(unsigned long) - 1" byte padding hole here. */ 286 }; 287 288 /* Test if STRUCTLEAK is clearing structs with __user fields. */ 289 struct test_user { 290 u8 one; 291 unsigned long two; 292 char __user *three; 293 unsigned long four; 294 }; 295 296 #define ALWAYS_PASS WANT_SUCCESS 297 #define ALWAYS_FAIL XFAIL 298 299 #ifdef CONFIG_INIT_STACK_NONE 300 # define USER_PASS XFAIL 301 # define BYREF_PASS XFAIL 302 # define STRONG_PASS XFAIL 303 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER) 304 # define USER_PASS WANT_SUCCESS 305 # define BYREF_PASS XFAIL 306 # define STRONG_PASS XFAIL 307 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF) 308 # define USER_PASS WANT_SUCCESS 309 # define BYREF_PASS WANT_SUCCESS 310 # define STRONG_PASS XFAIL 311 #else 312 # define USER_PASS WANT_SUCCESS 313 # define BYREF_PASS WANT_SUCCESS 314 # define STRONG_PASS WANT_SUCCESS 315 #endif 316 317 #define DEFINE_SCALAR_TEST(name, init, xfail) \ 318 DEFINE_TEST(name ## _ ## init, name, SCALAR, \ 319 init, xfail) 320 321 #define DEFINE_SCALAR_TESTS(init, xfail) \ 322 DEFINE_SCALAR_TEST(u8, init, xfail); \ 323 DEFINE_SCALAR_TEST(u16, init, xfail); \ 324 DEFINE_SCALAR_TEST(u32, init, xfail); \ 325 DEFINE_SCALAR_TEST(u64, init, xfail); \ 326 DEFINE_TEST(char_array_ ## init, unsigned char, \ 327 STRING, init, xfail) 328 329 #define DEFINE_STRUCT_TEST(name, init, xfail) \ 330 DEFINE_TEST(name ## _ ## init, \ 331 struct test_ ## name, STRUCT, init, \ 332 xfail) 333 334 #define DEFINE_STRUCT_TESTS(init, xfail) \ 335 DEFINE_STRUCT_TEST(small_hole, init, xfail); \ 336 DEFINE_STRUCT_TEST(big_hole, init, xfail); \ 337 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \ 338 DEFINE_STRUCT_TEST(packed, init, xfail) 339 340 #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \ 341 DEFINE_STRUCT_TESTS(base ## _ ## partial, \ 342 xfail); \ 343 DEFINE_STRUCT_TESTS(base ## _ ## all, xfail) 344 345 /* These should be fully initialized all the time! */ 346 DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS); 347 DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS); 348 /* Struct initializers: padding may be left uninitialized. */ 349 DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS); 350 DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS); 351 DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS); 352 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS); 353 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS); 354 DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL); 355 /* No initialization without compiler instrumentation. */ 356 DEFINE_SCALAR_TESTS(none, STRONG_PASS); 357 DEFINE_STRUCT_TESTS(none, BYREF_PASS); 358 /* Initialization of members with __user attribute. */ 359 DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS); 360 361 /* 362 * Check two uses through a variable declaration outside either path, 363 * which was noticed as a special case in porting earlier stack init 364 * compiler logic. 365 */ 366 static int noinline __leaf_switch_none(int path, bool fill) 367 { 368 switch (path) { 369 /* 370 * This is intentionally unreachable. To silence the 371 * warning, build with -Wno-switch-unreachable 372 */ 373 uint64_t var[10]; 374 375 case 1: 376 target_start = &var; 377 target_size = sizeof(var); 378 if (fill) { 379 fill_start = &var; 380 fill_size = sizeof(var); 381 382 memset(fill_start, forced_mask | 0x55, fill_size); 383 } 384 memcpy(check_buf, target_start, target_size); 385 break; 386 case 2: 387 target_start = &var; 388 target_size = sizeof(var); 389 if (fill) { 390 fill_start = &var; 391 fill_size = sizeof(var); 392 393 memset(fill_start, forced_mask | 0xaa, fill_size); 394 } 395 memcpy(check_buf, target_start, target_size); 396 break; 397 default: 398 var[1] = 5; 399 return var[1] & forced_mask; 400 } 401 return 0; 402 } 403 404 static noinline int leaf_switch_1_none(unsigned long sp, bool fill, 405 uint64_t *arg) 406 { 407 return __leaf_switch_none(1, fill); 408 } 409 410 static noinline int leaf_switch_2_none(unsigned long sp, bool fill, 411 uint64_t *arg) 412 { 413 return __leaf_switch_none(2, fill); 414 } 415 416 /* 417 * These are expected to fail for most configurations because neither 418 * GCC nor Clang have a way to perform initialization of variables in 419 * non-code areas (i.e. in a switch statement before the first "case"). 420 * https://llvm.org/pr44916 421 */ 422 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL); 423 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL); 424 425 #define KUNIT_test_scalars(init) \ 426 KUNIT_CASE(test_u8_ ## init), \ 427 KUNIT_CASE(test_u16_ ## init), \ 428 KUNIT_CASE(test_u32_ ## init), \ 429 KUNIT_CASE(test_u64_ ## init), \ 430 KUNIT_CASE(test_char_array_ ## init) 431 432 #define KUNIT_test_structs(init) \ 433 KUNIT_CASE(test_small_hole_ ## init), \ 434 KUNIT_CASE(test_big_hole_ ## init), \ 435 KUNIT_CASE(test_trailing_hole_ ## init),\ 436 KUNIT_CASE(test_packed_ ## init) \ 437 438 static struct kunit_case stackinit_test_cases[] = { 439 /* These are explicitly initialized and should always pass. */ 440 KUNIT_test_scalars(zero), 441 KUNIT_test_structs(zero), 442 /* Padding here appears to be accidentally always initialized? */ 443 KUNIT_test_structs(dynamic_partial), 444 KUNIT_test_structs(assigned_dynamic_partial), 445 /* Padding initialization depends on compiler behaviors. */ 446 KUNIT_test_structs(static_partial), 447 KUNIT_test_structs(static_all), 448 KUNIT_test_structs(dynamic_all), 449 KUNIT_test_structs(runtime_partial), 450 KUNIT_test_structs(runtime_all), 451 KUNIT_test_structs(assigned_static_partial), 452 KUNIT_test_structs(assigned_static_all), 453 KUNIT_test_structs(assigned_dynamic_all), 454 /* Everything fails this since it effectively performs a memcpy(). */ 455 KUNIT_test_structs(assigned_copy), 456 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */ 457 KUNIT_test_scalars(none), 458 KUNIT_CASE(test_switch_1_none), 459 KUNIT_CASE(test_switch_2_none), 460 /* STRUCTLEAK_BYREF should cover from here down. */ 461 KUNIT_test_structs(none), 462 /* STRUCTLEAK will only cover this. */ 463 KUNIT_CASE(test_user), 464 {} 465 }; 466 467 static struct kunit_suite stackinit_test_suite = { 468 .name = "stackinit", 469 .test_cases = stackinit_test_cases, 470 }; 471 472 kunit_test_suites(&stackinit_test_suite); 473 474 MODULE_DESCRIPTION("Test cases for compiler-based stack variable zeroing"); 475 MODULE_LICENSE("GPL"); 476