lib/test_stackinit.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  *
   6  * External build example:
   7  *      clang -O2 -Wall -ftrivial-auto-var-init=pattern \
   8  *              -o test_stackinit test_stackinit.c
   9  */
  10 #ifdef __KERNEL__
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/string.h>
  17
  18 #else
  19
  20 /* Userspace headers. */
  21 #include <stdio.h>
  22 #include <stdint.h>
  23 #include <string.h>
  24 #include <stdbool.h>
  25 #include <errno.h>
  26 #include <sys/types.h>
  27
  28 /* Linux kernel-ism stubs for stand-alone userspace build. */
  29 #define KBUILD_MODNAME          "stackinit"
  30 #define pr_fmt(fmt)             KBUILD_MODNAME ": " fmt
  31 #define pr_err(fmt, ...)        fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
  32 #define pr_warn(fmt, ...)       fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
  33 #define pr_info(fmt, ...)       fprintf(stdout, pr_fmt(fmt), ##__VA_ARGS__)
  34 #define __init                  /**/
  35 #define __exit                  /**/
  36 #define __user                  /**/
  37 #define noinline                __attribute__((__noinline__))
  38 #define __aligned(x)            __attribute__((__aligned__(x)))
  39 #ifdef __clang__
  40 # define __compiletime_error(message) /**/
  41 #else
  42 # define __compiletime_error(message) __attribute__((__error__(message)))
  43 #endif
  44 #define __compiletime_assert(condition, msg, prefix, suffix)            \
  45         do {                                                            \
  46                 extern void prefix ## suffix(void) __compiletime_error(msg); \
  47                 if (!(condition))                                       \
  48                         prefix ## suffix();                             \
  49         } while (0)
  50 #define _compiletime_assert(condition, msg, prefix, suffix) \
  51         __compiletime_assert(condition, msg, prefix, suffix)
  52 #define compiletime_assert(condition, msg) \
  53         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
  54 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
  55 #define BUILD_BUG_ON(condition) \
  56         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
  57 typedef uint8_t                 u8;
  58 typedef uint16_t                u16;
  59 typedef uint32_t                u32;
  60 typedef uint64_t                u64;
  61
  62 #define module_init(func)       static int (*do_init)(void) = func
  63 #define module_exit(func)       static void (*do_exit)(void) = func
  64 #define MODULE_LICENSE(str)     int main(void) {                \
  65                                         int rc;                 \
  66                                         /* License: str */      \
  67                                         rc = do_init();         \
  68                                         if (rc == 0)            \
  69                                                 do_exit();      \
  70                                         return rc;              \
  71                                 }
  72
  73 #endif /* __KERNEL__ */
  74
  75 /* Exfiltration buffer. */
  76 #define MAX_VAR_SIZE    128
  77 static u8 check_buf[MAX_VAR_SIZE];
  78
  79 /* Character array to trigger stack protector in all functions. */
  80 #define VAR_BUFFER       32
  81
  82 /* Volatile mask to convince compiler to copy memory with 0xff. */
  83 static volatile u8 forced_mask = 0xff;
  84
  85 /* Location and size tracking to validate fill and test are colocated. */
  86 static void *fill_start, *target_start;
  87 static size_t fill_size, target_size;
  88
  89 static bool range_contains(char *haystack_start, size_t haystack_size,
  90                            char *needle_start, size_t needle_size)
  91 {
  92         if (needle_start >= haystack_start &&
  93             needle_start + needle_size <= haystack_start + haystack_size)
  94                 return true;
  95         return false;
  96 }
  97
  98 /* Whether the test is expected to fail. */
  99 #define WANT_SUCCESS                            0
 100 #define XFAIL                                   1
 101
 102 #define DO_NOTHING_TYPE_SCALAR(var_type)        var_type
 103 #define DO_NOTHING_TYPE_STRING(var_type)        void
 104 #define DO_NOTHING_TYPE_STRUCT(var_type)        void
 105
 106 #define DO_NOTHING_RETURN_SCALAR(ptr)           *(ptr)
 107 #define DO_NOTHING_RETURN_STRING(ptr)           /**/
 108 #define DO_NOTHING_RETURN_STRUCT(ptr)           /**/
 109
 110 #define DO_NOTHING_CALL_SCALAR(var, name)                       \
 111                 (var) = do_nothing_ ## name(&(var))
 112 #define DO_NOTHING_CALL_STRING(var, name)                       \
 113                 do_nothing_ ## name(var)
 114 #define DO_NOTHING_CALL_STRUCT(var, name)                       \
 115                 do_nothing_ ## name(&(var))
 116
 117 #define FETCH_ARG_SCALAR(var)           &var
 118 #define FETCH_ARG_STRING(var)           var
 119 #define FETCH_ARG_STRUCT(var)           &var
 120
 121 #define FILL_SIZE_STRING                16
 122
 123 #define INIT_CLONE_SCALAR               /**/
 124 #define INIT_CLONE_STRING               [FILL_SIZE_STRING]
 125 #define INIT_CLONE_STRUCT               /**/
 126
 127 #define ZERO_CLONE_SCALAR(zero)         memset(&(zero), 0x00, sizeof(zero))
 128 #define ZERO_CLONE_STRING(zero)         memset(&(zero), 0x00, sizeof(zero))
 129 /*
 130  * For the struct, intentionally poison padding to see if it gets
 131  * copied out in direct assignments.
 132  * */
 133 #define ZERO_CLONE_STRUCT(zero)                         \
 134         do {                                            \
 135                 memset(&(zero), 0xFF, sizeof(zero));    \
 136                 zero.one = 0;                           \
 137                 zero.two = 0;                           \
 138                 zero.three = 0;                         \
 139                 zero.four = 0;                          \
 140         } while (0)
 141
 142 #define INIT_SCALAR_none(var_type)      /**/
 143 #define INIT_SCALAR_zero(var_type)      = 0
 144
 145 #define INIT_STRING_none(var_type)      [FILL_SIZE_STRING] /**/
 146 #define INIT_STRING_zero(var_type)      [FILL_SIZE_STRING] = { }
 147
 148 #define INIT_STRUCT_none(var_type)      /**/
 149 #define INIT_STRUCT_zero(var_type)      = { }
 150
 151
 152 #define __static_partial                { .two = 0, }
 153 #define __static_all                    { .one = 0,                     \
 154                                           .two = 0,                     \
 155                                           .three = 0,                   \
 156                                           .four = 0,                    \
 157                                         }
 158 #define __dynamic_partial               { .two = arg->two, }
 159 #define __dynamic_all                   { .one = arg->one,              \
 160                                           .two = arg->two,              \
 161                                           .three = arg->three,          \
 162                                           .four = arg->four,            \
 163                                         }
 164 #define __runtime_partial               var.two = 0
 165 #define __runtime_all                   var.one = 0;                    \
 166                                         var.two = 0;                    \
 167                                         var.three = 0;                  \
 168                                         var.four = 0
 169
 170 #define INIT_STRUCT_static_partial(var_type)                            \
 171                                         = __static_partial
 172 #define INIT_STRUCT_static_all(var_type)                                \
 173                                         = __static_all
 174 #define INIT_STRUCT_dynamic_partial(var_type)                           \
 175                                         = __dynamic_partial
 176 #define INIT_STRUCT_dynamic_all(var_type)                               \
 177                                         = __dynamic_all
 178 #define INIT_STRUCT_runtime_partial(var_type)                           \
 179                                         ; __runtime_partial
 180 #define INIT_STRUCT_runtime_all(var_type)                               \
 181                                         ; __runtime_all
 182
 183 #define INIT_STRUCT_assigned_static_partial(var_type)                   \
 184                                         ; var = (var_type)__static_partial
 185 #define INIT_STRUCT_assigned_static_all(var_type)                       \
 186                                         ; var = (var_type)__static_all
 187 #define INIT_STRUCT_assigned_dynamic_partial(var_type)                  \
 188                                         ; var = (var_type)__dynamic_partial
 189 #define INIT_STRUCT_assigned_dynamic_all(var_type)                      \
 190                                         ; var = (var_type)__dynamic_all
 191
 192 #define INIT_STRUCT_assigned_copy(var_type)                             \
 193                                         ; var = *(arg)
 194
 195 /*
 196  * @name: unique string name for the test
 197  * @var_type: type to be tested for zeroing initialization
 198  * @which: is this a SCALAR, STRING, or STRUCT type?
 199  * @init_level: what kind of initialization is performed
 200  * @xfail: is this test expected to fail?
 201  */
 202 #define DEFINE_TEST_DRIVER(name, var_type, which, xfail)        \
 203 /* Returns 0 on success, 1 on failure. */                       \
 204 static noinline __init int test_ ## name (void)                 \
 205 {                                                               \
 206         var_type zero INIT_CLONE_ ## which;                     \
 207         int ignored;                                            \
 208         u8 sum = 0, i;                                          \
 209                                                                 \
 210         /* Notice when a new test is larger than expected. */   \
 211         BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);              \
 212                                                                 \
 213         /* Fill clone type with zero for per-field init. */     \
 214         ZERO_CLONE_ ## which(zero);                             \
 215         /* Clear entire check buffer for 0xFF overlap test. */  \
 216         memset(check_buf, 0x00, sizeof(check_buf));             \
 217         /* Fill stack with 0xFF. */                             \
 218         ignored = leaf_ ##name((unsigned long)&ignored, 1,      \
 219                                 FETCH_ARG_ ## which(zero));     \
 220         /* Verify all bytes overwritten with 0xFF. */           \
 221         for (sum = 0, i = 0; i < target_size; i++)              \
 222                 sum += (check_buf[i] != 0xFF);                  \
 223         if (sum) {                                              \
 224                 pr_err(#name ": leaf fill was not 0xFF!?\n");   \
 225                 return 1;                                       \
 226         }                                                       \
 227         /* Clear entire check buffer for later bit tests. */    \
 228         memset(check_buf, 0x00, sizeof(check_buf));             \
 229         /* Extract stack-defined variable contents. */          \
 230         ignored = leaf_ ##name((unsigned long)&ignored, 0,      \
 231                                 FETCH_ARG_ ## which(zero));     \
 232                                                                 \
 233         /* Validate that compiler lined up fill and target. */  \
 234         if (!range_contains(fill_start, fill_size,              \
 235                             target_start, target_size)) {       \
 236                 pr_err(#name ": stack fill missed target!?\n"); \
 237                 pr_err(#name ": fill %zu wide\n", fill_size);   \
 238                 pr_err(#name ": target offset by %d\n", \
 239                         (int)((ssize_t)(uintptr_t)fill_start -  \
 240                         (ssize_t)(uintptr_t)target_start));     \
 241                 return 1;                                       \
 242         }                                                       \
 243                                                                 \
 244         /* Look for any bytes still 0xFF in check region. */    \
 245         for (sum = 0, i = 0; i < target_size; i++)              \
 246                 sum += (check_buf[i] == 0xFF);                  \
 247                                                                 \
 248         if (sum == 0) {                                         \
 249                 pr_info(#name " ok\n");                         \
 250                 return 0;                                       \
 251         } else {                                                \
 252                 pr_warn(#name " %sFAIL (uninit bytes: %d)\n",   \
 253                         (xfail) ? "X" : "", sum);               \
 254                 return (xfail) ? 0 : 1;                         \
 255         }                                                       \
 256 }
 257 #define DEFINE_TEST(name, var_type, which, init_level, xfail)   \
 258 /* no-op to force compiler into ignoring "uninitialized" vars */\
 259 static noinline __init DO_NOTHING_TYPE_ ## which(var_type)      \
 260 do_nothing_ ## name(var_type *ptr)                              \
 261 {                                                               \
 262         /* Will always be true, but compiler doesn't know. */   \
 263         if ((unsigned long)ptr > 0x2)                           \
 264                 return DO_NOTHING_RETURN_ ## which(ptr);        \
 265         else                                                    \
 266                 return DO_NOTHING_RETURN_ ## which(ptr + 1);    \
 267 }                                                               \
 268 static noinline __init int leaf_ ## name(unsigned long sp,      \
 269                                          bool fill,             \
 270                                          var_type *arg)         \
 271 {                                                               \
 272         char buf[VAR_BUFFER];                                   \
 273         var_type var                                            \
 274                 INIT_ ## which ## _ ## init_level(var_type);    \
 275                                                                 \
 276         target_start = &var;                                    \
 277         target_size = sizeof(var);                              \
 278         /*                                                      \
 279          * Keep this buffer around to make sure we've got a     \
 280          * stack frame of SOME kind...                          \
 281          */                                                     \
 282         memset(buf, (char)(sp & 0xff), sizeof(buf));            \
 283         /* Fill variable with 0xFF. */                          \
 284         if (fill) {                                             \
 285                 fill_start = &var;                              \
 286                 fill_size = sizeof(var);                        \
 287                 memset(fill_start,                              \
 288                        (char)((sp & 0xff) | forced_mask),       \
 289                        fill_size);                              \
 290         }                                                       \
 291                                                                 \
 292         /* Silence "never initialized" warnings. */             \
 293         DO_NOTHING_CALL_ ## which(var, name);                   \
 294                                                                 \
 295         /* Exfiltrate "var". */                                 \
 296         memcpy(check_buf, target_start, target_size);           \
 297                                                                 \
 298         return (int)buf[0] | (int)buf[sizeof(buf) - 1];         \
 299 }                                                               \
 300 DEFINE_TEST_DRIVER(name, var_type, which, xfail)
 301
 302 /* Structure with no padding. */
 303 struct test_packed {
 304         unsigned long one;
 305         unsigned long two;
 306         unsigned long three;
 307         unsigned long four;
 308 };
 309
 310 /* Simple structure with padding likely to be covered by compiler. */
 311 struct test_small_hole {
 312         size_t one;
 313         char two;
 314         /* 3 byte padding hole here. */
 315         int three;
 316         unsigned long four;
 317 };
 318
 319 /* Trigger unhandled padding in a structure. */
 320 struct test_big_hole {
 321         u8 one;
 322         u8 two;
 323         u8 three;
 324         /* 61 byte padding hole here. */
 325         u8 four __aligned(64);
 326 } __aligned(64);
 327
 328 struct test_trailing_hole {
 329         char *one;
 330         char *two;
 331         char *three;
 332         char four;
 333         /* "sizeof(unsigned long) - 1" byte padding hole here. */
 334 };
 335
 336 /* Test if STRUCTLEAK is clearing structs with __user fields. */
 337 struct test_user {
 338         u8 one;
 339         unsigned long two;
 340         char __user *three;
 341         unsigned long four;
 342 };
 343
 344 #define DEFINE_SCALAR_TEST(name, init, xfail)                   \
 345                 DEFINE_TEST(name ## _ ## init, name, SCALAR,    \
 346                             init, xfail)
 347
 348 #define DEFINE_SCALAR_TESTS(init, xfail)                        \
 349                 DEFINE_SCALAR_TEST(u8, init, xfail);            \
 350                 DEFINE_SCALAR_TEST(u16, init, xfail);           \
 351                 DEFINE_SCALAR_TEST(u32, init, xfail);           \
 352                 DEFINE_SCALAR_TEST(u64, init, xfail);           \
 353                 DEFINE_TEST(char_array_ ## init, unsigned char, \
 354                             STRING, init, xfail)
 355
 356 #define DEFINE_STRUCT_TEST(name, init, xfail)                   \
 357                 DEFINE_TEST(name ## _ ## init,                  \
 358                             struct test_ ## name, STRUCT, init, \
 359                             xfail)
 360
 361 #define DEFINE_STRUCT_TESTS(init, xfail)                        \
 362                 DEFINE_STRUCT_TEST(small_hole, init, xfail);    \
 363                 DEFINE_STRUCT_TEST(big_hole, init, xfail);      \
 364                 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
 365                 DEFINE_STRUCT_TEST(packed, init, xfail)
 366
 367 #define DEFINE_STRUCT_INITIALIZER_TESTS(base)                   \
 368                 DEFINE_STRUCT_TESTS(base ## _ ## partial,       \
 369                                     WANT_SUCCESS);              \
 370                 DEFINE_STRUCT_TESTS(base ## _ ## all,           \
 371                                     WANT_SUCCESS)
 372
 373 /* These should be fully initialized all the time! */
 374 DEFINE_SCALAR_TESTS(zero, WANT_SUCCESS);
 375 DEFINE_STRUCT_TESTS(zero, WANT_SUCCESS);
 376 /* Struct initializers: padding may be left uninitialized. */
 377 DEFINE_STRUCT_INITIALIZER_TESTS(static);
 378 DEFINE_STRUCT_INITIALIZER_TESTS(dynamic);
 379 DEFINE_STRUCT_INITIALIZER_TESTS(runtime);
 380 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static);
 381 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic);
 382 DEFINE_STRUCT_TESTS(assigned_copy, XFAIL);
 383 /* No initialization without compiler instrumentation. */
 384 DEFINE_SCALAR_TESTS(none, WANT_SUCCESS);
 385 DEFINE_STRUCT_TESTS(none, WANT_SUCCESS);
 386 /* Initialization of members with __user attribute. */
 387 DEFINE_TEST(user, struct test_user, STRUCT, none, WANT_SUCCESS);
 388
 389 /*
 390  * Check two uses through a variable declaration outside either path,
 391  * which was noticed as a special case in porting earlier stack init
 392  * compiler logic.
 393  */
 394 static int noinline __leaf_switch_none(int path, bool fill)
 395 {
 396         switch (path) {
 397                 /*
 398                  * This is intentionally unreachable. To silence the
 399                  * warning, build with -Wno-switch-unreachable
 400                  */
 401                 uint64_t var;
 402
 403         case 1:
 404                 target_start = &var;
 405                 target_size = sizeof(var);
 406                 if (fill) {
 407                         fill_start = &var;
 408                         fill_size = sizeof(var);
 409
 410                         memset(fill_start, forced_mask | 0x55, fill_size);
 411                 }
 412                 memcpy(check_buf, target_start, target_size);
 413                 break;
 414         case 2:
 415                 target_start = &var;
 416                 target_size = sizeof(var);
 417                 if (fill) {
 418                         fill_start = &var;
 419                         fill_size = sizeof(var);
 420
 421                         memset(fill_start, forced_mask | 0xaa, fill_size);
 422                 }
 423                 memcpy(check_buf, target_start, target_size);
 424                 break;
 425         default:
 426                 var = 5;
 427                 return var & forced_mask;
 428         }
 429         return 0;
 430 }
 431
 432 static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
 433                                               uint64_t *arg)
 434 {
 435         return __leaf_switch_none(1, fill);
 436 }
 437
 438 static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
 439                                               uint64_t *arg)
 440 {
 441         return __leaf_switch_none(2, fill);
 442 }
 443
 444 /*
 445  * These are expected to fail for most configurations because neither
 446  * GCC nor Clang have a way to perform initialization of variables in
 447  * non-code areas (i.e. in a switch statement before the first "case").
 448  * https://bugs.llvm.org/show_bug.cgi?id=44916
 449  */
 450 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, XFAIL);
 451 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, XFAIL);
 452
 453 static int __init test_stackinit_init(void)
 454 {
 455         unsigned int failures = 0;
 456
 457 #define test_scalars(init)      do {                            \
 458                 failures += test_u8_ ## init ();                \
 459                 failures += test_u16_ ## init ();               \
 460                 failures += test_u32_ ## init ();               \
 461                 failures += test_u64_ ## init ();               \
 462                 failures += test_char_array_ ## init ();        \
 463         } while (0)
 464
 465 #define test_structs(init)      do {                            \
 466                 failures += test_small_hole_ ## init ();        \
 467                 failures += test_big_hole_ ## init ();          \
 468                 failures += test_trailing_hole_ ## init ();     \
 469                 failures += test_packed_ ## init ();            \
 470         } while (0)
 471
 472         /* These are explicitly initialized and should always pass. */
 473         test_scalars(zero);
 474         test_structs(zero);
 475         /* Padding here appears to be accidentally always initialized? */
 476         test_structs(dynamic_partial);
 477         test_structs(assigned_dynamic_partial);
 478         /* Padding initialization depends on compiler behaviors. */
 479         test_structs(static_partial);
 480         test_structs(static_all);
 481         test_structs(dynamic_all);
 482         test_structs(runtime_partial);
 483         test_structs(runtime_all);
 484         test_structs(assigned_static_partial);
 485         test_structs(assigned_static_all);
 486         test_structs(assigned_dynamic_all);
 487         /* Everything fails this since it effectively performs a memcpy(). */
 488         test_structs(assigned_copy);
 489
 490         /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
 491         test_scalars(none);
 492         failures += test_switch_1_none();
 493         failures += test_switch_2_none();
 494
 495         /* STRUCTLEAK_BYREF should cover from here down. */
 496         test_structs(none);
 497
 498         /* STRUCTLEAK will only cover this. */
 499         failures += test_user();
 500
 501         if (failures == 0)
 502                 pr_info("all tests passed!\n");
 503         else
 504                 pr_err("failures: %u\n", failures);
 505
 506         return failures ? -EINVAL : 0;
 507 }
 508 module_init(test_stackinit_init);
 509
 510 static void __exit test_stackinit_exit(void)
 511 { }
 512 module_exit(test_stackinit_exit);
 513
 514 MODULE_LICENSE("GPL");