smatch_buf_size.c

   1 /*
   2  * smatch/smatch_buf_size.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include <stdlib.h>
  11 #include <errno.h>
  12 #include "parse.h"
  13 #include "smatch.h"
  14 #include "smatch_slist.h"
  15 #include "smatch_extra.h"
  16
  17 /*
  18  * This check has two smatch IDs.
  19  * my_size_id - used to store the size of arrays.
  20  * my_strlen_id - track the strlen() of buffers.
  21  */
  22
  23 static int my_size_id;
  24 static int my_strlen_id;
  25
  26 struct limiter {
  27         int buf_arg;
  28         int limit_arg;
  29 };
  30 static struct limiter b0_l2 = {0, 2};
  31
  32 static _Bool params_set[32];
  33
  34 static void set_undefined(struct sm_state *sm)
  35 {
  36         if (sm->state != &undefined)
  37                 set_state(sm->owner, sm->name, sm->sym, &undefined);
  38 }
  39
  40 void set_param_buf_size(const char *name, struct symbol *sym, char *key, char *value)
  41 {
  42         char fullname[256];
  43         unsigned int size;
  44
  45         if (strncmp(key, "$$", 2))
  46                 return;
  47
  48         snprintf(fullname, 256, "%s%s", name, key + 2);
  49
  50         errno = 0;
  51         size = strtoul(value, NULL, 10);
  52         if (errno)
  53                 return;
  54
  55         set_state(my_size_id, fullname, sym, alloc_state_num(size));
  56 }
  57
  58 static int bytes_per_element(struct expression *expr)
  59 {
  60         struct symbol *type;
  61         int bpe;
  62
  63         if (expr->type == EXPR_STRING)
  64                 return 1;
  65         type = get_type(expr);
  66         if (!type)
  67                 return 0;
  68
  69         if (type->type != SYM_PTR && type->type != SYM_ARRAY)
  70                 return 0;
  71
  72         type = get_base_type(type);
  73         bpe = bits_to_bytes(type->bit_size);
  74
  75         if (bpe == -1) /* void pointer */
  76                 bpe = 1;
  77
  78         return bpe;
  79 }
  80
  81 static int bytes_to_elements(struct expression *expr, int bytes)
  82 {
  83         int bpe;
  84
  85         bpe = bytes_per_element(expr);
  86         if (bpe == 0)
  87                 return 0;
  88         return bytes / bpe;
  89 }
  90
  91 static int elements_to_bytes(struct expression *expr, int elements)
  92 {
  93         int bpe;
  94
  95         bpe = bytes_per_element(expr);
  96         return elements * bpe;
  97 }
  98
  99 static int get_initializer_size(struct expression *expr)
 100 {
 101         switch (expr->type) {
 102         case EXPR_STRING:
 103                 return expr->string->length;
 104         case EXPR_INITIALIZER: {
 105                 struct expression *tmp;
 106                 int i = 0;
 107                 int max = 0;
 108
 109                 FOR_EACH_PTR(expr->expr_list, tmp) {
 110                         if (tmp->type == EXPR_INDEX && tmp->idx_to > max)
 111                                 max = tmp->idx_to;
 112                         i++;
 113                 } END_FOR_EACH_PTR(tmp);
 114                 if (max)
 115                         return max + 1;
 116                 return i;
 117         }
 118         case EXPR_SYMBOL:
 119                 return get_array_size(expr);
 120         }
 121         return 0;
 122 }
 123
 124 static int db_size;
 125 static int db_size_callback(void *unused, int argc, char **argv, char **azColName)
 126 {
 127         if (db_size == 0)
 128                 db_size = atoi(argv[0]);
 129         else
 130                 db_size = -1;
 131         return 0;
 132 }
 133
 134 static int size_from_db(struct expression *expr)
 135 {
 136         char *name;
 137
 138         if (!option_spammy)
 139                 return 0;
 140
 141         name = get_member_name(expr);
 142         if (!name)
 143                 return 0;
 144
 145         db_size = 0;
 146         run_sql(db_size_callback, "select size from type_size where type = '%s' and file = '%s'",
 147                         name, get_filename());
 148         if (db_size == -1)
 149                 return 0;
 150         if (db_size != 0)
 151                 return db_size;
 152
 153         run_sql(db_size_callback, "select size from type_size where type = '%s'",
 154                         name);
 155
 156         if (db_size == -1)
 157                 db_size = 0;
 158
 159         return db_size;
 160 }
 161
 162 static int get_real_array_size(struct expression *expr)
 163 {
 164         struct symbol *type;
 165         int ret;
 166
 167         if (expr->type == EXPR_BINOP) /* array elements foo[5] */
 168                 return 0;
 169
 170         type = get_type(expr);
 171         if (!type || type->type != SYM_ARRAY)
 172                 return 0;
 173
 174         ret = get_expression_value(type->array_size);
 175         /* Dynamically sized array are -1 in sparse */
 176         if (ret <= 0)
 177                 return 0;
 178         /* People put one element arrays on the end of structs */
 179         if (ret == 1)
 180                 return 0;
 181
 182         return ret;
 183 }
 184
 185 static int get_size_from_initializer(struct expression *expr)
 186 {
 187         if (expr->type != EXPR_SYMBOL || !expr->symbol->initializer)
 188                 return 0;
 189         if (expr->symbol->initializer == expr) /* int a = a; */
 190                 return 0;
 191         return get_initializer_size(expr->symbol->initializer);
 192 }
 193
 194 static int get_stored_size_bytes(struct expression *expr)
 195 {
 196         struct smatch_state *state;
 197
 198         state = get_state_expr(my_size_id, expr);
 199         if (!state)
 200                 return 0;
 201         return PTR_INT(state->data);
 202 }
 203
 204 static int get_bytes_from_address(struct expression *expr)
 205 {
 206         struct symbol *type;
 207         int ret;
 208
 209         if (!option_spammy)
 210                 return 0;
 211         if (expr->type != EXPR_PREOP || expr->op != '&')
 212                 return 0;
 213         type = get_type(expr);
 214         if (!type)
 215                 return 0;
 216
 217         if (type->type == SYM_PTR)
 218                 type = get_base_type(type);
 219
 220         ret = bits_to_bytes(type->bit_size);
 221         if (ret == -1)
 222                 return 0;
 223         if (ret == 1)
 224                 return 0;  /* ignore char pointers */
 225
 226         return ret;
 227 }
 228
 229 static int get_size_from_strlen(struct expression *expr)
 230 {
 231         struct smatch_state *state;
 232         long long len;
 233
 234         state = get_state_expr(my_strlen_id, expr);
 235         if (!state || !state->data)
 236                 return 0;
 237         if (get_implied_max((struct expression *)state->data, &len))
 238                 return len + 1; /* add one because strlen doesn't include the NULL */
 239         return 0;
 240 }
 241
 242 static struct expression *remove_addr_fluff(struct expression *expr)
 243 {
 244         struct expression *tmp;
 245         long long val;
 246
 247         expr = strip_expr(expr);
 248
 249         /* remove '&' and '*' operations that cancel */
 250         while (expr->type == EXPR_PREOP && expr->op == '&') {
 251                 tmp = strip_expr(expr->unop);
 252                 if (tmp->type != EXPR_PREOP)
 253                         break;
 254                 if (tmp->op != '*')
 255                         break;
 256                 expr = strip_expr(tmp->unop);
 257         }
 258
 259         /* "foo + 0" is just "foo" */
 260         if (expr->type == EXPR_BINOP && expr->op == '+' &&
 261             get_value(expr->right, &val) && val == 0)
 262                 return expr->left;
 263
 264         return expr;
 265 }
 266
 267 int get_array_size_bytes(struct expression *expr)
 268 {
 269         int size;
 270
 271         expr = remove_addr_fluff(expr);
 272         if (!expr)
 273                 return 0;
 274
 275         /* strcpy(foo, "BAR"); */
 276         if (expr->type == EXPR_STRING)
 277                 return expr->string->length;
 278
 279         /* buf[4] */
 280         size = get_real_array_size(expr);
 281         if (size)
 282                 return elements_to_bytes(expr, size);
 283
 284         /* buf = malloc(1024); */
 285         size = get_stored_size_bytes(expr);
 286         if (size)
 287                 return size;
 288
 289         /* char *foo = "BAR" */
 290         size = get_size_from_initializer(expr);
 291         if (size)
 292                 return elements_to_bytes(expr, size);
 293
 294         size = get_bytes_from_address(expr);
 295         if (size)
 296                 return size;
 297
 298         /* if (strlen(foo) > 4) */
 299         size = get_size_from_strlen(expr);
 300         if (size)
 301                 return size;
 302
 303         return size_from_db(expr);
 304 }
 305
 306 int get_array_size(struct expression *expr)
 307 {
 308         int bytes;
 309
 310         bytes = get_array_size_bytes(expr);
 311         return bytes_to_elements(expr, bytes);
 312 }
 313
 314 static void match_strlen_condition(struct expression *expr)
 315 {
 316         struct expression *left;
 317         struct expression *right;
 318         struct expression *str = NULL;
 319         int strlen_left = 0;
 320         int strlen_right = 0;
 321         long long val;
 322         struct smatch_state *true_state = NULL;
 323         struct smatch_state *false_state = NULL;
 324
 325         if (expr->type != EXPR_COMPARE)
 326                 return;
 327         left = strip_expr(expr->left);
 328         right = strip_expr(expr->right);
 329
 330         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 331                 str = get_argument_from_call_expr(left->args, 0);
 332                 strlen_left = 1;
 333         }
 334         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 335                 str = get_argument_from_call_expr(right->args, 0);
 336                 strlen_right = 1;
 337         }
 338
 339         if (!strlen_left && !strlen_right)
 340                 return;
 341         if (strlen_left && strlen_right)
 342                 return;
 343
 344         if (strlen_left) {
 345                 if (!get_value(right, &val))
 346                         return;
 347         }
 348         if (strlen_right) {
 349                 if (!get_value(left, &val))
 350                         return;
 351         }
 352
 353         if (expr->op == SPECIAL_EQUAL) {
 354                 set_true_false_states_expr(my_size_id, str, alloc_state_num(val + 1), NULL);
 355                 return;
 356         }
 357         if (expr->op == SPECIAL_NOTEQUAL) {
 358                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(val + 1));
 359                 return;
 360         }
 361
 362         switch (expr->op) {
 363         case '<':
 364         case SPECIAL_UNSIGNED_LT:
 365                 if (strlen_left)
 366                         true_state = alloc_state_num(val);
 367                 else
 368                         false_state = alloc_state_num(val + 1);
 369                 break;
 370         case SPECIAL_LTE:
 371         case SPECIAL_UNSIGNED_LTE:
 372                 if (strlen_left)
 373                         true_state = alloc_state_num(val + 1);
 374                 else
 375                         false_state = alloc_state_num(val);
 376                 break;
 377         case SPECIAL_GTE:
 378         case SPECIAL_UNSIGNED_GTE:
 379                 if (strlen_left)
 380                         false_state = alloc_state_num(val);
 381                 else
 382                         true_state = alloc_state_num(val + 1);
 383                 break;
 384         case '>':
 385         case SPECIAL_UNSIGNED_GT:
 386                 if (strlen_left)
 387                         false_state = alloc_state_num(val + 1);
 388                 else
 389                         true_state = alloc_state_num(val);
 390                 break;
 391         }
 392         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 393 }
 394
 395 static struct expression *strip_ampersands(struct expression *expr)
 396 {
 397         struct symbol *type;
 398
 399         if (expr->type != EXPR_PREOP)
 400                 return expr;
 401         if (expr->op != '&')
 402                 return expr;
 403         type = get_type(expr->unop);
 404         if (!type || type->type != SYM_ARRAY)
 405                 return expr;
 406         return expr->unop;
 407 }
 408
 409 static void match_array_assignment(struct expression *expr)
 410 {
 411         struct expression *left;
 412         struct expression *right;
 413         int array_size;
 414
 415         if (expr->op != '=')
 416                 return;
 417         left = strip_expr(expr->left);
 418         right = strip_expr(expr->right);
 419         right = strip_ampersands(right);
 420         array_size = get_array_size_bytes(right);
 421         if (array_size)
 422                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 423 }
 424
 425 static void info_record_alloction(struct expression *buffer, struct expression *size)
 426 {
 427         char *member;
 428         long long val;
 429
 430         if (!option_info)
 431                 return;
 432         member = get_member_name(buffer);
 433         if (!member)
 434                 return;
 435         if (!get_implied_value(size, &val))
 436                 val = -1;
 437         sm_msg("info: '%s' allocated_buf_size %lld", member, val);
 438         free_string(member);
 439 }
 440
 441 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 442 {
 443         int size_arg = PTR_INT(_size_arg);
 444         struct expression *right;
 445         struct expression *arg;
 446         long long bytes;
 447
 448         right = strip_expr(expr->right);
 449         arg = get_argument_from_call_expr(right->args, size_arg);
 450
 451         info_record_alloction(expr->left, arg);
 452
 453         if (!get_implied_value(arg, &bytes))
 454                 return;
 455         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes));
 456 }
 457
 458 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 459 {
 460         struct expression *right;
 461         struct expression *arg;
 462         long long elements;
 463         long long size;
 464
 465         right = strip_expr(expr->right);
 466         arg = get_argument_from_call_expr(right->args, 0);
 467         if (!get_implied_value(arg, &elements))
 468                 return;
 469         arg = get_argument_from_call_expr(right->args, 1);
 470         if (!get_implied_value(arg, &size))
 471                 return;
 472         set_state_expr(my_size_id, expr->left, alloc_state_num(elements * size));
 473 }
 474
 475 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 476 {
 477         struct expression *right;
 478         struct expression *str;
 479         struct expression *len_expr;
 480         char *len_name;
 481         struct smatch_state *state;
 482
 483         right = strip_expr(expr->right);
 484         str = get_argument_from_call_expr(right->args, 0);
 485         len_expr = strip_expr(expr->left);
 486
 487         len_name = get_variable_from_expr(len_expr, NULL);
 488         if (!len_name)
 489                 return;
 490
 491         state = __alloc_smatch_state(0);
 492         state->name = len_name;
 493         state->data = len_expr;
 494         set_state_expr(my_strlen_id, str, state);
 495 }
 496
 497 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 498 {
 499         struct limiter *limiter = (struct limiter *)_limiter;
 500         struct expression *dest;
 501         struct expression *size_expr;
 502         long long size;
 503
 504         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 505         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 506         if (!get_implied_max(size_expr, &size))
 507                 return;
 508         set_state_expr(my_size_id, dest, alloc_state_num(size));
 509 }
 510
 511 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 512 {
 513         struct expression fake_assign;
 514
 515         fake_assign.op = '=';
 516         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 517         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 518         match_array_assignment(&fake_assign);
 519 }
 520
 521 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 522 {
 523         struct expression *fn_expr;
 524         struct expression *size_expr;
 525         long long size;
 526
 527         fn_expr = strip_expr(expr->right);
 528         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 529         if (!get_implied_max(size_expr, &size))
 530                 return;
 531
 532         /* It's easy to forget space for the NUL char */
 533         size++;
 534         set_state_expr(my_size_id, expr->left, alloc_state_num(size));
 535 }
 536
 537 static void match_call(struct expression *expr)
 538 {
 539         char *name;
 540         struct expression *arg;
 541         int bytes;
 542         int i;
 543
 544         name = get_fnptr_name(expr->fn);
 545         if (!name)
 546                 return;
 547
 548         i = 0;
 549         FOR_EACH_PTR(expr->args, arg) {
 550                 bytes = get_array_size_bytes(arg);
 551                 if (bytes > 1)
 552                         sm_msg("info: passes_buffer '%s' %d '$$' %d %s",
 553                                 name, i, bytes,
 554                                 is_static(expr->fn) ? "static" : "global");
 555                 i++;
 556         } END_FOR_EACH_PTR(arg);
 557
 558         free_string(name);
 559 }
 560
 561 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 562 {
 563         if (state == &merged)
 564                 return;
 565         sm_msg("info: passes_buffer '%s' %d '%s' %s %s", fn, param, printed_name, state->name, global_static);
 566 }
 567
 568 static void match_func_end(struct symbol *sym)
 569 {
 570         memset(params_set, 0, sizeof(params_set));
 571 }
 572
 573 void register_buf_size(int id)
 574 {
 575         my_size_id = id;
 576
 577         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 578
 579         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 580         add_function_assign_hook("calloc", &match_calloc, NULL);
 581         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 582         if (option_project == PROJ_KERNEL) {
 583                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 584                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 585                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 586                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 587                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 588                 add_function_assign_hook("kmalloc_array", &match_calloc, NULL);
 589                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 590                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 591                 add_function_assign_hook("sock_kmalloc", &match_alloc, INT_PTR(1));
 592                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 593                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 594         }
 595         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 596         add_hook(&match_strlen_condition, CONDITION_HOOK);
 597         add_function_assign_hook("strlen", &match_strlen, NULL);
 598
 599         add_function_assign_hook("strndup", match_strndup, NULL);
 600         if (option_project == PROJ_KERNEL)
 601                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 602
 603         add_hook(&match_func_end, END_FUNC_HOOK);
 604         add_modification_hook(my_size_id, &set_undefined);
 605 }
 606
 607 void register_strlen(int id)
 608 {
 609         my_strlen_id = id;
 610         add_modification_hook(my_strlen_id, &set_undefined);
 611 }
 612
 613 void register_buf_size_late(int id)
 614 {
 615         add_function_hook("strlcpy", &match_limited, &b0_l2);
 616         add_function_hook("strlcat", &match_limited, &b0_l2);
 617         add_function_hook("memscan", &match_limited, &b0_l2);
 618
 619         add_function_hook("strcpy", &match_strcpy, NULL);
 620
 621         if (option_info) {
 622                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 623                 add_member_info_callback(my_size_id, struct_member_callback);
 624         }
 625 }