Masahiro Yamada | 8e82fe2 | 2019-06-01 12:22:42 +0900 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0 |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 2 | /* |
| 3 | * Test cases for compiler-based stack variable zeroing via future |
| 4 | * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*. |
| 5 | */ |
| 6 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 7 | |
| 8 | #include <linux/init.h> |
| 9 | #include <linux/kernel.h> |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/string.h> |
| 12 | |
| 13 | /* Exfiltration buffer. */ |
| 14 | #define MAX_VAR_SIZE 128 |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 15 | static u8 check_buf[MAX_VAR_SIZE]; |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 16 | |
| 17 | /* Character array to trigger stack protector in all functions. */ |
| 18 | #define VAR_BUFFER 32 |
| 19 | |
| 20 | /* Volatile mask to convince compiler to copy memory with 0xff. */ |
| 21 | static volatile u8 forced_mask = 0xff; |
| 22 | |
| 23 | /* Location and size tracking to validate fill and test are colocated. */ |
| 24 | static void *fill_start, *target_start; |
| 25 | static size_t fill_size, target_size; |
| 26 | |
| 27 | static bool range_contains(char *haystack_start, size_t haystack_size, |
| 28 | char *needle_start, size_t needle_size) |
| 29 | { |
| 30 | if (needle_start >= haystack_start && |
| 31 | needle_start + needle_size <= haystack_start + haystack_size) |
| 32 | return true; |
| 33 | return false; |
| 34 | } |
| 35 | |
| 36 | #define DO_NOTHING_TYPE_SCALAR(var_type) var_type |
| 37 | #define DO_NOTHING_TYPE_STRING(var_type) void |
| 38 | #define DO_NOTHING_TYPE_STRUCT(var_type) void |
| 39 | |
| 40 | #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr) |
| 41 | #define DO_NOTHING_RETURN_STRING(ptr) /**/ |
| 42 | #define DO_NOTHING_RETURN_STRUCT(ptr) /**/ |
| 43 | |
| 44 | #define DO_NOTHING_CALL_SCALAR(var, name) \ |
| 45 | (var) = do_nothing_ ## name(&(var)) |
| 46 | #define DO_NOTHING_CALL_STRING(var, name) \ |
| 47 | do_nothing_ ## name(var) |
| 48 | #define DO_NOTHING_CALL_STRUCT(var, name) \ |
| 49 | do_nothing_ ## name(&(var)) |
| 50 | |
| 51 | #define FETCH_ARG_SCALAR(var) &var |
| 52 | #define FETCH_ARG_STRING(var) var |
| 53 | #define FETCH_ARG_STRUCT(var) &var |
| 54 | |
| 55 | #define FILL_SIZE_STRING 16 |
| 56 | |
| 57 | #define INIT_CLONE_SCALAR /**/ |
| 58 | #define INIT_CLONE_STRING [FILL_SIZE_STRING] |
| 59 | #define INIT_CLONE_STRUCT /**/ |
| 60 | |
| 61 | #define INIT_SCALAR_none /**/ |
| 62 | #define INIT_SCALAR_zero = 0 |
| 63 | |
| 64 | #define INIT_STRING_none [FILL_SIZE_STRING] /**/ |
| 65 | #define INIT_STRING_zero [FILL_SIZE_STRING] = { } |
| 66 | |
| 67 | #define INIT_STRUCT_none /**/ |
| 68 | #define INIT_STRUCT_zero = { } |
| 69 | #define INIT_STRUCT_static_partial = { .two = 0, } |
| 70 | #define INIT_STRUCT_static_all = { .one = arg->one, \ |
| 71 | .two = arg->two, \ |
| 72 | .three = arg->three, \ |
| 73 | .four = arg->four, \ |
| 74 | } |
| 75 | #define INIT_STRUCT_dynamic_partial = { .two = arg->two, } |
| 76 | #define INIT_STRUCT_dynamic_all = { .one = arg->one, \ |
| 77 | .two = arg->two, \ |
| 78 | .three = arg->three, \ |
| 79 | .four = arg->four, \ |
| 80 | } |
| 81 | #define INIT_STRUCT_runtime_partial ; \ |
| 82 | var.two = 0 |
| 83 | #define INIT_STRUCT_runtime_all ; \ |
| 84 | var.one = 0; \ |
| 85 | var.two = 0; \ |
| 86 | var.three = 0; \ |
| 87 | memset(&var.four, 0, \ |
| 88 | sizeof(var.four)) |
| 89 | |
| 90 | /* |
| 91 | * @name: unique string name for the test |
| 92 | * @var_type: type to be tested for zeroing initialization |
| 93 | * @which: is this a SCALAR, STRING, or STRUCT type? |
| 94 | * @init_level: what kind of initialization is performed |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 95 | * @xfail: is this test expected to fail? |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 96 | */ |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 97 | #define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 98 | /* Returns 0 on success, 1 on failure. */ \ |
| 99 | static noinline __init int test_ ## name (void) \ |
| 100 | { \ |
| 101 | var_type zero INIT_CLONE_ ## which; \ |
| 102 | int ignored; \ |
| 103 | u8 sum = 0, i; \ |
| 104 | \ |
| 105 | /* Notice when a new test is larger than expected. */ \ |
| 106 | BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \ |
| 107 | \ |
| 108 | /* Fill clone type with zero for per-field init. */ \ |
| 109 | memset(&zero, 0x00, sizeof(zero)); \ |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 110 | /* Clear entire check buffer for 0xFF overlap test. */ \ |
| 111 | memset(check_buf, 0x00, sizeof(check_buf)); \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 112 | /* Fill stack with 0xFF. */ \ |
| 113 | ignored = leaf_ ##name((unsigned long)&ignored, 1, \ |
| 114 | FETCH_ARG_ ## which(zero)); \ |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 115 | /* Verify all bytes overwritten with 0xFF. */ \ |
| 116 | for (sum = 0, i = 0; i < target_size; i++) \ |
| 117 | sum += (check_buf[i] != 0xFF); \ |
| 118 | if (sum) { \ |
| 119 | pr_err(#name ": leaf fill was not 0xFF!?\n"); \ |
| 120 | return 1; \ |
| 121 | } \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 122 | /* Clear entire check buffer for later bit tests. */ \ |
| 123 | memset(check_buf, 0x00, sizeof(check_buf)); \ |
| 124 | /* Extract stack-defined variable contents. */ \ |
| 125 | ignored = leaf_ ##name((unsigned long)&ignored, 0, \ |
| 126 | FETCH_ARG_ ## which(zero)); \ |
| 127 | \ |
| 128 | /* Validate that compiler lined up fill and target. */ \ |
| 129 | if (!range_contains(fill_start, fill_size, \ |
| 130 | target_start, target_size)) { \ |
| 131 | pr_err(#name ": stack fill missed target!?\n"); \ |
| 132 | pr_err(#name ": fill %zu wide\n", fill_size); \ |
| 133 | pr_err(#name ": target offset by %d\n", \ |
| 134 | (int)((ssize_t)(uintptr_t)fill_start - \ |
| 135 | (ssize_t)(uintptr_t)target_start)); \ |
| 136 | return 1; \ |
| 137 | } \ |
| 138 | \ |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 139 | /* Look for any bytes still 0xFF in check region. */ \ |
| 140 | for (sum = 0, i = 0; i < target_size; i++) \ |
| 141 | sum += (check_buf[i] == 0xFF); \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 142 | \ |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 143 | if (sum == 0) { \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 144 | pr_info(#name " ok\n"); \ |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 145 | return 0; \ |
| 146 | } else { \ |
| 147 | pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \ |
| 148 | (xfail) ? "X" : "", sum); \ |
| 149 | return (xfail) ? 0 : 1; \ |
| 150 | } \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 151 | } |
| 152 | #define DEFINE_TEST(name, var_type, which, init_level) \ |
| 153 | /* no-op to force compiler into ignoring "uninitialized" vars */\ |
| 154 | static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \ |
| 155 | do_nothing_ ## name(var_type *ptr) \ |
| 156 | { \ |
| 157 | /* Will always be true, but compiler doesn't know. */ \ |
| 158 | if ((unsigned long)ptr > 0x2) \ |
| 159 | return DO_NOTHING_RETURN_ ## which(ptr); \ |
| 160 | else \ |
| 161 | return DO_NOTHING_RETURN_ ## which(ptr + 1); \ |
| 162 | } \ |
| 163 | static noinline __init int leaf_ ## name(unsigned long sp, \ |
| 164 | bool fill, \ |
| 165 | var_type *arg) \ |
| 166 | { \ |
| 167 | char buf[VAR_BUFFER]; \ |
| 168 | var_type var INIT_ ## which ## _ ## init_level; \ |
| 169 | \ |
| 170 | target_start = &var; \ |
| 171 | target_size = sizeof(var); \ |
| 172 | /* \ |
| 173 | * Keep this buffer around to make sure we've got a \ |
| 174 | * stack frame of SOME kind... \ |
| 175 | */ \ |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 176 | memset(buf, (char)(sp & 0xff), sizeof(buf)); \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 177 | /* Fill variable with 0xFF. */ \ |
| 178 | if (fill) { \ |
| 179 | fill_start = &var; \ |
| 180 | fill_size = sizeof(var); \ |
| 181 | memset(fill_start, \ |
Kees Cook | 8c30d32 | 2019-06-04 22:13:59 -0700 | [diff] [blame] | 182 | (char)((sp & 0xff) | forced_mask), \ |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 183 | fill_size); \ |
| 184 | } \ |
| 185 | \ |
| 186 | /* Silence "never initialized" warnings. */ \ |
| 187 | DO_NOTHING_CALL_ ## which(var, name); \ |
| 188 | \ |
| 189 | /* Exfiltrate "var". */ \ |
| 190 | memcpy(check_buf, target_start, target_size); \ |
| 191 | \ |
| 192 | return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \ |
| 193 | } \ |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 194 | DEFINE_TEST_DRIVER(name, var_type, which, 0) |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 195 | |
| 196 | /* Structure with no padding. */ |
| 197 | struct test_packed { |
| 198 | unsigned long one; |
| 199 | unsigned long two; |
| 200 | unsigned long three; |
| 201 | unsigned long four; |
| 202 | }; |
| 203 | |
| 204 | /* Simple structure with padding likely to be covered by compiler. */ |
| 205 | struct test_small_hole { |
| 206 | size_t one; |
| 207 | char two; |
| 208 | /* 3 byte padding hole here. */ |
| 209 | int three; |
| 210 | unsigned long four; |
| 211 | }; |
| 212 | |
| 213 | /* Try to trigger unhandled padding in a structure. */ |
| 214 | struct test_aligned { |
| 215 | u32 internal1; |
| 216 | u64 internal2; |
| 217 | } __aligned(64); |
| 218 | |
| 219 | struct test_big_hole { |
| 220 | u8 one; |
| 221 | u8 two; |
| 222 | u8 three; |
| 223 | /* 61 byte padding hole here. */ |
| 224 | struct test_aligned four; |
| 225 | } __aligned(64); |
| 226 | |
| 227 | struct test_trailing_hole { |
| 228 | char *one; |
| 229 | char *two; |
| 230 | char *three; |
| 231 | char four; |
| 232 | /* "sizeof(unsigned long) - 1" byte padding hole here. */ |
| 233 | }; |
| 234 | |
| 235 | /* Test if STRUCTLEAK is clearing structs with __user fields. */ |
| 236 | struct test_user { |
| 237 | u8 one; |
| 238 | unsigned long two; |
| 239 | char __user *three; |
| 240 | unsigned long four; |
| 241 | }; |
| 242 | |
| 243 | #define DEFINE_SCALAR_TEST(name, init) \ |
| 244 | DEFINE_TEST(name ## _ ## init, name, SCALAR, init) |
| 245 | |
| 246 | #define DEFINE_SCALAR_TESTS(init) \ |
| 247 | DEFINE_SCALAR_TEST(u8, init); \ |
| 248 | DEFINE_SCALAR_TEST(u16, init); \ |
| 249 | DEFINE_SCALAR_TEST(u32, init); \ |
| 250 | DEFINE_SCALAR_TEST(u64, init); \ |
| 251 | DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init) |
| 252 | |
| 253 | #define DEFINE_STRUCT_TEST(name, init) \ |
| 254 | DEFINE_TEST(name ## _ ## init, \ |
| 255 | struct test_ ## name, STRUCT, init) |
| 256 | |
| 257 | #define DEFINE_STRUCT_TESTS(init) \ |
| 258 | DEFINE_STRUCT_TEST(small_hole, init); \ |
| 259 | DEFINE_STRUCT_TEST(big_hole, init); \ |
| 260 | DEFINE_STRUCT_TEST(trailing_hole, init); \ |
| 261 | DEFINE_STRUCT_TEST(packed, init) |
| 262 | |
| 263 | /* These should be fully initialized all the time! */ |
| 264 | DEFINE_SCALAR_TESTS(zero); |
| 265 | DEFINE_STRUCT_TESTS(zero); |
| 266 | /* Static initialization: padding may be left uninitialized. */ |
| 267 | DEFINE_STRUCT_TESTS(static_partial); |
| 268 | DEFINE_STRUCT_TESTS(static_all); |
| 269 | /* Dynamic initialization: padding may be left uninitialized. */ |
| 270 | DEFINE_STRUCT_TESTS(dynamic_partial); |
| 271 | DEFINE_STRUCT_TESTS(dynamic_all); |
| 272 | /* Runtime initialization: padding may be left uninitialized. */ |
| 273 | DEFINE_STRUCT_TESTS(runtime_partial); |
| 274 | DEFINE_STRUCT_TESTS(runtime_all); |
| 275 | /* No initialization without compiler instrumentation. */ |
| 276 | DEFINE_SCALAR_TESTS(none); |
| 277 | DEFINE_STRUCT_TESTS(none); |
| 278 | DEFINE_TEST(user, struct test_user, STRUCT, none); |
| 279 | |
| 280 | /* |
| 281 | * Check two uses through a variable declaration outside either path, |
| 282 | * which was noticed as a special case in porting earlier stack init |
| 283 | * compiler logic. |
| 284 | */ |
| 285 | static int noinline __leaf_switch_none(int path, bool fill) |
| 286 | { |
| 287 | switch (path) { |
| 288 | uint64_t var; |
| 289 | |
| 290 | case 1: |
| 291 | target_start = &var; |
| 292 | target_size = sizeof(var); |
| 293 | if (fill) { |
| 294 | fill_start = &var; |
| 295 | fill_size = sizeof(var); |
| 296 | |
| 297 | memset(fill_start, forced_mask | 0x55, fill_size); |
| 298 | } |
| 299 | memcpy(check_buf, target_start, target_size); |
| 300 | break; |
| 301 | case 2: |
| 302 | target_start = &var; |
| 303 | target_size = sizeof(var); |
| 304 | if (fill) { |
| 305 | fill_start = &var; |
| 306 | fill_size = sizeof(var); |
| 307 | |
| 308 | memset(fill_start, forced_mask | 0xaa, fill_size); |
| 309 | } |
| 310 | memcpy(check_buf, target_start, target_size); |
| 311 | break; |
| 312 | default: |
| 313 | var = 5; |
| 314 | return var & forced_mask; |
| 315 | } |
| 316 | return 0; |
| 317 | } |
| 318 | |
| 319 | static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill, |
| 320 | uint64_t *arg) |
| 321 | { |
| 322 | return __leaf_switch_none(1, fill); |
| 323 | } |
| 324 | |
| 325 | static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill, |
| 326 | uint64_t *arg) |
| 327 | { |
| 328 | return __leaf_switch_none(2, fill); |
| 329 | } |
| 330 | |
Kees Cook | 9cf016e | 2020-04-06 20:10:12 -0700 | [diff] [blame] | 331 | /* |
| 332 | * These are expected to fail for most configurations because neither |
| 333 | * GCC nor Clang have a way to perform initialization of variables in |
| 334 | * non-code areas (i.e. in a switch statement before the first "case"). |
| 335 | * https://bugs.llvm.org/show_bug.cgi?id=44916 |
| 336 | */ |
| 337 | DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, 1); |
| 338 | DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, 1); |
Kees Cook | 50ceaa95e | 2019-01-23 12:24:32 -0700 | [diff] [blame] | 339 | |
| 340 | static int __init test_stackinit_init(void) |
| 341 | { |
| 342 | unsigned int failures = 0; |
| 343 | |
| 344 | #define test_scalars(init) do { \ |
| 345 | failures += test_u8_ ## init (); \ |
| 346 | failures += test_u16_ ## init (); \ |
| 347 | failures += test_u32_ ## init (); \ |
| 348 | failures += test_u64_ ## init (); \ |
| 349 | failures += test_char_array_ ## init (); \ |
| 350 | } while (0) |
| 351 | |
| 352 | #define test_structs(init) do { \ |
| 353 | failures += test_small_hole_ ## init (); \ |
| 354 | failures += test_big_hole_ ## init (); \ |
| 355 | failures += test_trailing_hole_ ## init (); \ |
| 356 | failures += test_packed_ ## init (); \ |
| 357 | } while (0) |
| 358 | |
| 359 | /* These are explicitly initialized and should always pass. */ |
| 360 | test_scalars(zero); |
| 361 | test_structs(zero); |
| 362 | /* Padding here appears to be accidentally always initialized? */ |
| 363 | test_structs(dynamic_partial); |
| 364 | /* Padding initialization depends on compiler behaviors. */ |
| 365 | test_structs(static_partial); |
| 366 | test_structs(static_all); |
| 367 | test_structs(dynamic_all); |
| 368 | test_structs(runtime_partial); |
| 369 | test_structs(runtime_all); |
| 370 | |
| 371 | /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */ |
| 372 | test_scalars(none); |
| 373 | failures += test_switch_1_none(); |
| 374 | failures += test_switch_2_none(); |
| 375 | |
| 376 | /* STRUCTLEAK_BYREF should cover from here down. */ |
| 377 | test_structs(none); |
| 378 | |
| 379 | /* STRUCTLEAK will only cover this. */ |
| 380 | failures += test_user(); |
| 381 | |
| 382 | if (failures == 0) |
| 383 | pr_info("all tests passed!\n"); |
| 384 | else |
| 385 | pr_err("failures: %u\n", failures); |
| 386 | |
| 387 | return failures ? -EINVAL : 0; |
| 388 | } |
| 389 | module_init(test_stackinit_init); |
| 390 | |
| 391 | static void __exit test_stackinit_exit(void) |
| 392 | { } |
| 393 | module_exit(test_stackinit_exit); |
| 394 | |
| 395 | MODULE_LICENSE("GPL"); |