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 #define FILL_SIZE_STRING                16
  67
  68 #define INIT_CLONE_SCALAR               /**/
  69 #define INIT_CLONE_STRING               [FILL_SIZE_STRING]
  70 #define INIT_CLONE_STRUCT               /**/
  71
  72 #define ZERO_CLONE_SCALAR(zero)         memset(&(zero), 0x00, sizeof(zero))
  73 #define ZERO_CLONE_STRING(zero)         memset(&(zero), 0x00, sizeof(zero))
  74 /*
  75  * For the struct, intentionally poison padding to see if it gets
  76  * copied out in direct assignments.
  77  * */
  78 #define ZERO_CLONE_STRUCT(zero)                         \
  79         do {                                            \
  80                 memset(&(zero), 0xFF, sizeof(zero));    \
  81                 zero.one = 0;                           \
  82                 zero.two = 0;                           \
  83                 zero.three = 0;                         \
  84                 zero.four = 0;                          \
  85         } while (0)
  86
  87 #define INIT_SCALAR_none(var_type)      /**/
  88 #define INIT_SCALAR_zero(var_type)      = 0
  89
  90 #define INIT_STRING_none(var_type)      [FILL_SIZE_STRING] /**/
  91 #define INIT_STRING_zero(var_type)      [FILL_SIZE_STRING] = { }
  92
  93 #define INIT_STRUCT_none(var_type)      /**/
  94 #define INIT_STRUCT_zero(var_type)      = { }
  95
  96
  97 #define __static_partial                { .two = 0, }
  98 #define __static_all                    { .one = 0,                     \
  99                                           .two = 0,                     \
 100                                           .three = 0,                   \
 101                                           .four = 0,                    \
 102                                         }
 103 #define __dynamic_partial               { .two = arg->two, }
 104 #define __dynamic_all                   { .one = arg->one,              \
 105                                           .two = arg->two,              \
 106                                           .three = arg->three,          \
 107                                           .four = arg->four,            \
 108                                         }
 109 #define __runtime_partial               var.two = 0
 110 #define __runtime_all                   var.one = 0;                    \
 111                                         var.two = 0;                    \
 112                                         var.three = 0;                  \
 113                                         var.four = 0
 114
 115 #define INIT_STRUCT_static_partial(var_type)                            \
 116                                         = __static_partial
 117 #define INIT_STRUCT_static_all(var_type)                                \
 118                                         = __static_all
 119 #define INIT_STRUCT_dynamic_partial(var_type)                           \
 120                                         = __dynamic_partial
 121 #define INIT_STRUCT_dynamic_all(var_type)                               \
 122                                         = __dynamic_all
 123 #define INIT_STRUCT_runtime_partial(var_type)                           \
 124                                         ; __runtime_partial
 125 #define INIT_STRUCT_runtime_all(var_type)                               \
 126                                         ; __runtime_all
 127
 128 #define INIT_STRUCT_assigned_static_partial(var_type)                   \
 129                                         ; var = (var_type)__static_partial
 130 #define INIT_STRUCT_assigned_static_all(var_type)                       \
 131                                         ; var = (var_type)__static_all
 132 #define INIT_STRUCT_assigned_dynamic_partial(var_type)                  \
 133                                         ; var = (var_type)__dynamic_partial
 134 #define INIT_STRUCT_assigned_dynamic_all(var_type)                      \
 135                                         ; var = (var_type)__dynamic_all
 136
 137 #define INIT_STRUCT_assigned_copy(var_type)                             \
 138                                         ; var = *(arg)
 139
 140 /*
 141  * @name: unique string name for the test
 142  * @var_type: type to be tested for zeroing initialization
 143  * @which: is this a SCALAR, STRING, or STRUCT type?
 144  * @init_level: what kind of initialization is performed
 145  * @xfail: is this test expected to fail?
 146  */
 147 #define DEFINE_TEST_DRIVER(name, var_type, which, xfail)        \
 148 /* Returns 0 on success, 1 on failure. */                       \
 149 static noinline void test_ ## name (struct kunit *test)         \
 150 {                                                               \
 151         var_type zero INIT_CLONE_ ## which;                     \
 152         int ignored;                                            \
 153         u8 sum = 0, i;                                          \
 154                                                                 \
 155         /* Notice when a new test is larger than expected. */   \
 156         BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);              \
 157                                                                 \
 158         /* Fill clone type with zero for per-field init. */     \
 159         ZERO_CLONE_ ## which(zero);                             \
 160         /* Clear entire check buffer for 0xFF overlap test. */  \
 161         memset(check_buf, 0x00, sizeof(check_buf));             \
 162         /* Fill stack with 0xFF. */                             \
 163         ignored = leaf_ ##name((unsigned long)&ignored, 1,      \
 164                                 FETCH_ARG_ ## which(zero));     \
 165         /* Verify all bytes overwritten with 0xFF. */           \
 166         for (sum = 0, i = 0; i < target_size; i++)              \
 167                 sum += (check_buf[i] != 0xFF);                  \
 168         KUNIT_ASSERT_EQ_MSG(test, sum, 0,                       \
 169                             "leaf fill was not 0xFF!?\n");      \
 170         /* Clear entire check buffer for later bit tests. */    \
 171         memset(check_buf, 0x00, sizeof(check_buf));             \
 172         /* Extract stack-defined variable contents. */          \
 173         ignored = leaf_ ##name((unsigned long)&ignored, 0,      \
 174                                 FETCH_ARG_ ## which(zero));     \
 175                                                                 \
 176         /* Validate that compiler lined up fill and target. */  \
 177         KUNIT_ASSERT_TRUE_MSG(test,                             \
 178                 stackinit_range_contains(fill_start, fill_size, \
 179                             target_start, target_size),         \
 180                 "stack fill missed target!? "                   \
 181                 "(fill %zu wide, target offset by %d)\n",       \
 182                 fill_size,                                      \
 183                 (int)((ssize_t)(uintptr_t)fill_start -          \
 184                       (ssize_t)(uintptr_t)target_start));       \
 185                                                                 \
 186         /* Look for any bytes still 0xFF in check region. */    \
 187         for (sum = 0, i = 0; i < target_size; i++)              \
 188                 sum += (check_buf[i] == 0xFF);                  \
 189                                                                 \
 190         if (sum != 0 && xfail)                                  \
 191                 kunit_skip(test,                                \
 192                            "XFAIL uninit bytes: %d\n",          \
 193                            sum);                                \
 194         KUNIT_ASSERT_EQ_MSG(test, sum, 0,                       \
 195                 "uninit bytes: %d\n", sum);                     \
 196 }
 197 #define DEFINE_TEST(name, var_type, which, init_level, xfail)   \
 198 /* no-op to force compiler into ignoring "uninitialized" vars */\
 199 static noinline DO_NOTHING_TYPE_ ## which(var_type)             \
 200 do_nothing_ ## name(var_type *ptr)                              \
 201 {                                                               \
 202         /* Will always be true, but compiler doesn't know. */   \
 203         if ((unsigned long)ptr > 0x2)                           \
 204                 return DO_NOTHING_RETURN_ ## which(ptr);        \
 205         else                                                    \
 206                 return DO_NOTHING_RETURN_ ## which(ptr + 1);    \
 207 }                                                               \
 208 static noinline int leaf_ ## name(unsigned long sp, bool fill,  \
 209                                   var_type *arg)                \
 210 {                                                               \
 211         char buf[VAR_BUFFER];                                   \
 212         var_type var                                            \
 213                 INIT_ ## which ## _ ## init_level(var_type);    \
 214                                                                 \
 215         target_start = &var;                                    \
 216         target_size = sizeof(var);                              \
 217         /*                                                      \
 218          * Keep this buffer around to make sure we've got a     \
 219          * stack frame of SOME kind...                          \
 220          */                                                     \
 221         memset(buf, (char)(sp & 0xff), sizeof(buf));            \
 222         /* Fill variable with 0xFF. */                          \
 223         if (fill) {                                             \
 224                 fill_start = &var;                              \
 225                 fill_size = sizeof(var);                        \
 226                 memset(fill_start,                              \
 227                        (char)((sp & 0xff) | forced_mask),       \
 228                        fill_size);                              \
 229         }                                                       \
 230                                                                 \
 231         /* Silence "never initialized" warnings. */             \
 232         DO_NOTHING_CALL_ ## which(var, name);                   \
 233                                                                 \
 234         /* Exfiltrate "var". */                                 \
 235         memcpy(check_buf, target_start, target_size);           \
 236                                                                 \
 237         return (int)buf[0] | (int)buf[sizeof(buf) - 1];         \
 238 }                                                               \
 239 DEFINE_TEST_DRIVER(name, var_type, which, xfail)
 240
 241 /* Structure with no padding. */
 242 struct test_packed {
 243         unsigned long one;
 244         unsigned long two;
 245         unsigned long three;
 246         unsigned long four;
 247 };
 248
 249 /* Simple structure with padding likely to be covered by compiler. */
 250 struct test_small_hole {
 251         size_t one;
 252         char two;
 253         /* 3 byte padding hole here. */
 254         int three;
 255         unsigned long four;
 256 };
 257
 258 /* Trigger unhandled padding in a structure. */
 259 struct test_big_hole {
 260         u8 one;
 261         u8 two;
 262         u8 three;
 263         /* 61 byte padding hole here. */
 264         u8 four __aligned(64);
 265 } __aligned(64);
 266
 267 struct test_trailing_hole {
 268         char *one;
 269         char *two;
 270         char *three;
 271         char four;
 272         /* "sizeof(unsigned long) - 1" byte padding hole here. */
 273 };
 274
 275 /* Test if STRUCTLEAK is clearing structs with __user fields. */
 276 struct test_user {
 277         u8 one;
 278         unsigned long two;
 279         char __user *three;
 280         unsigned long four;
 281 };
 282
 283 #define ALWAYS_PASS     WANT_SUCCESS
 284 #define ALWAYS_FAIL     XFAIL
 285
 286 #ifdef CONFIG_INIT_STACK_NONE
 287 # define USER_PASS      XFAIL
 288 # define BYREF_PASS     XFAIL
 289 # define STRONG_PASS    XFAIL
 290 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)
 291 # define USER_PASS      WANT_SUCCESS
 292 # define BYREF_PASS     XFAIL
 293 # define STRONG_PASS    XFAIL
 294 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)
 295 # define USER_PASS      WANT_SUCCESS
 296 # define BYREF_PASS     WANT_SUCCESS
 297 # define STRONG_PASS    XFAIL
 298 #else
 299 # define USER_PASS      WANT_SUCCESS
 300 # define BYREF_PASS     WANT_SUCCESS
 301 # define STRONG_PASS    WANT_SUCCESS
 302 #endif
 303
 304 #define DEFINE_SCALAR_TEST(name, init, xfail)                   \
 305                 DEFINE_TEST(name ## _ ## init, name, SCALAR,    \
 306                             init, xfail)
 307
 308 #define DEFINE_SCALAR_TESTS(init, xfail)                        \
 309                 DEFINE_SCALAR_TEST(u8, init, xfail);            \
 310                 DEFINE_SCALAR_TEST(u16, init, xfail);           \
 311                 DEFINE_SCALAR_TEST(u32, init, xfail);           \
 312                 DEFINE_SCALAR_TEST(u64, init, xfail);           \
 313                 DEFINE_TEST(char_array_ ## init, unsigned char, \
 314                             STRING, init, xfail)
 315
 316 #define DEFINE_STRUCT_TEST(name, init, xfail)                   \
 317                 DEFINE_TEST(name ## _ ## init,                  \
 318                             struct test_ ## name, STRUCT, init, \
 319                             xfail)
 320
 321 #define DEFINE_STRUCT_TESTS(init, xfail)                        \
 322                 DEFINE_STRUCT_TEST(small_hole, init, xfail);    \
 323                 DEFINE_STRUCT_TEST(big_hole, init, xfail);      \
 324                 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
 325                 DEFINE_STRUCT_TEST(packed, init, xfail)
 326
 327 #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail)            \
 328                 DEFINE_STRUCT_TESTS(base ## _ ## partial,       \
 329                                     xfail);                     \
 330                 DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)
 331
 332 /* These should be fully initialized all the time! */
 333 DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
 334 DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
 335 /* Struct initializers: padding may be left uninitialized. */
 336 DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
 337 DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
 338 DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
 339 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
 340 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
 341 DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
 342 /* No initialization without compiler instrumentation. */
 343 DEFINE_SCALAR_TESTS(none, STRONG_PASS);
 344 DEFINE_STRUCT_TESTS(none, BYREF_PASS);
 345 /* Initialization of members with __user attribute. */
 346 DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);
 347
 348 /*
 349  * Check two uses through a variable declaration outside either path,
 350  * which was noticed as a special case in porting earlier stack init
 351  * compiler logic.
 352  */
 353 static int noinline __leaf_switch_none(int path, bool fill)
 354 {
 355         switch (path) {
 356                 /*
 357                  * This is intentionally unreachable. To silence the
 358                  * warning, build with -Wno-switch-unreachable
 359                  */
 360                 uint64_t var[10];
 361
 362         case 1:
 363                 target_start = &var;
 364                 target_size = sizeof(var);
 365                 if (fill) {
 366                         fill_start = &var;
 367                         fill_size = sizeof(var);
 368
 369                         memset(fill_start, forced_mask | 0x55, fill_size);
 370                 }
 371                 memcpy(check_buf, target_start, target_size);
 372                 break;
 373         case 2:
 374                 target_start = &var;
 375                 target_size = sizeof(var);
 376                 if (fill) {
 377                         fill_start = &var;
 378                         fill_size = sizeof(var);
 379
 380                         memset(fill_start, forced_mask | 0xaa, fill_size);
 381                 }
 382                 memcpy(check_buf, target_start, target_size);
 383                 break;
 384         default:
 385                 var[1] = 5;
 386                 return var[1] & forced_mask;
 387         }
 388         return 0;
 389 }
 390
 391 static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
 392                                               uint64_t *arg)
 393 {
 394         return __leaf_switch_none(1, fill);
 395 }
 396
 397 static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
 398                                               uint64_t *arg)
 399 {
 400         return __leaf_switch_none(2, fill);
 401 }
 402
 403 /*
 404  * These are expected to fail for most configurations because neither
 405  * GCC nor Clang have a way to perform initialization of variables in
 406  * non-code areas (i.e. in a switch statement before the first "case").
 407  * https://bugs.llvm.org/show_bug.cgi?id=44916
 408  */
 409 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);
 410 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
 411
 412 #define KUNIT_test_scalars(init)                        \
 413                 KUNIT_CASE(test_u8_ ## init),           \
 414                 KUNIT_CASE(test_u16_ ## init),          \
 415                 KUNIT_CASE(test_u32_ ## init),          \
 416                 KUNIT_CASE(test_u64_ ## init),          \
 417                 KUNIT_CASE(test_char_array_ ## init)
 418
 419 #define KUNIT_test_structs(init)                        \
 420                 KUNIT_CASE(test_small_hole_ ## init),   \
 421                 KUNIT_CASE(test_big_hole_ ## init),     \
 422                 KUNIT_CASE(test_trailing_hole_ ## init),\
 423                 KUNIT_CASE(test_packed_ ## init)        \
 424
 425 static struct kunit_case stackinit_test_cases[] = {
 426         /* These are explicitly initialized and should always pass. */
 427         KUNIT_test_scalars(zero),
 428         KUNIT_test_structs(zero),
 429         /* Padding here appears to be accidentally always initialized? */
 430         KUNIT_test_structs(dynamic_partial),
 431         KUNIT_test_structs(assigned_dynamic_partial),
 432         /* Padding initialization depends on compiler behaviors. */
 433         KUNIT_test_structs(static_partial),
 434         KUNIT_test_structs(static_all),
 435         KUNIT_test_structs(dynamic_all),
 436         KUNIT_test_structs(runtime_partial),
 437         KUNIT_test_structs(runtime_all),
 438         KUNIT_test_structs(assigned_static_partial),
 439         KUNIT_test_structs(assigned_static_all),
 440         KUNIT_test_structs(assigned_dynamic_all),
 441         /* Everything fails this since it effectively performs a memcpy(). */
 442         KUNIT_test_structs(assigned_copy),
 443         /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
 444         KUNIT_test_scalars(none),
 445         KUNIT_CASE(test_switch_1_none),
 446         KUNIT_CASE(test_switch_2_none),
 447         /* STRUCTLEAK_BYREF should cover from here down. */
 448         KUNIT_test_structs(none),
 449         /* STRUCTLEAK will only cover this. */
 450         KUNIT_CASE(test_user),
 451         {}
 452 };
 453
 454 static struct kunit_suite stackinit_test_suite = {
 455         .name = "stackinit",
 456         .test_cases = stackinit_test_cases,
 457 };
 458
 459 kunit_test_suites(&stackinit_test_suite);
 460
 461 MODULE_LICENSE("GPL");