lib/stackinit_kunit.c

   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");