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 static struct smatch_state *merge_func(struct smatch_state *s1, struct smatch_state *s2)
  41 {
  42         if (PTR_INT(s1->data) == PTR_INT(s2->data))
  43                 return s1;
  44         return &undefined;
  45 }
  46
  47 void set_param_buf_size(const char *name, struct symbol *sym, char *key, char *value)
  48 {
  49         char fullname[256];
  50         unsigned int size;
  51
  52         if (strncmp(key, "$$", 2))
  53                 return;
  54
  55         snprintf(fullname, 256, "%s%s", name, key + 2);
  56
  57         errno = 0;
  58         size = strtoul(value, NULL, 10);
  59         if (errno)
  60                 return;
  61
  62         set_state(my_size_id, fullname, sym, alloc_state_num(size));
  63 }
  64
  65 static int bytes_per_element(struct expression *expr)
  66 {
  67         struct symbol *type;
  68         int bpe;
  69
  70         if (expr->type == EXPR_STRING)
  71                 return 1;
  72         type = get_type(expr);
  73         if (!type)
  74                 return 0;
  75
  76         if (type->type != SYM_PTR && type->type != SYM_ARRAY)
  77                 return 0;
  78
  79         type = get_base_type(type);
  80         bpe = bits_to_bytes(type->bit_size);
  81
  82         if (bpe == -1) /* void pointer */
  83                 bpe = 1;
  84
  85         return bpe;
  86 }
  87
  88 static int bytes_to_elements(struct expression *expr, int bytes)
  89 {
  90         int bpe;
  91
  92         bpe = bytes_per_element(expr);
  93         if (bpe == 0)
  94                 return 0;
  95         return bytes / bpe;
  96 }
  97
  98 static int elements_to_bytes(struct expression *expr, int elements)
  99 {
 100         int bpe;
 101
 102         bpe = bytes_per_element(expr);
 103         return elements * bpe;
 104 }
 105
 106 static int get_initializer_size(struct expression *expr)
 107 {
 108         switch (expr->type) {
 109         case EXPR_STRING:
 110                 return expr->string->length;
 111         case EXPR_INITIALIZER: {
 112                 struct expression *tmp;
 113                 int i = 0;
 114                 int max = 0;
 115
 116                 FOR_EACH_PTR(expr->expr_list, tmp) {
 117                         if (tmp->type == EXPR_INDEX && tmp->idx_to > max)
 118                                 max = tmp->idx_to;
 119                         i++;
 120                 } END_FOR_EACH_PTR(tmp);
 121                 if (max)
 122                         return max + 1;
 123                 return i;
 124         }
 125         case EXPR_SYMBOL:
 126                 return get_array_size(expr);
 127         }
 128         return 0;
 129 }
 130
 131 static int db_size;
 132 static int db_size_callback(void *unused, int argc, char **argv, char **azColName)
 133 {
 134         if (db_size == 0)
 135                 db_size = atoi(argv[0]);
 136         else
 137                 db_size = -1;
 138         return 0;
 139 }
 140
 141 static int size_from_db(struct expression *expr)
 142 {
 143         int this_file_only = 0;
 144         char *name;
 145
 146         if (!option_spammy)
 147                 return 0;
 148
 149         name = get_member_name(expr);
 150         if (!name && is_static(expr)) {
 151                 name = get_variable_from_expr(expr, NULL);
 152                 this_file_only = 1;
 153         }
 154         if (!name)
 155                 return 0;
 156
 157         db_size = 0;
 158         run_sql(db_size_callback, "select size from type_size where type = '%s' and file = '%s'",
 159                         name, get_filename());
 160         if (db_size == -1)
 161                 return 0;
 162         if (db_size != 0)
 163                 return db_size;
 164         if (this_file_only)
 165                 return 0;
 166
 167         run_sql(db_size_callback, "select size from type_size where type = '%s'",
 168                         name);
 169
 170         if (db_size == -1)
 171                 db_size = 0;
 172
 173         return db_size;
 174 }
 175
 176 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 177 {
 178         struct expression *call;
 179         sval_t sval;
 180
 181         if (expr->type != EXPR_ASSIGNMENT)
 182                 return;
 183         call = strip_expr(expr->right);
 184
 185         if (!parse_call_math_sval(call, math, &sval))
 186                 return;
 187         set_state_expr(my_size_id, expr->left, alloc_state_num(sval.value));
 188 }
 189
 190 static int get_real_array_size(struct expression *expr)
 191 {
 192         struct symbol *type;
 193         int ret;
 194
 195         if (expr->type == EXPR_BINOP) /* array elements foo[5] */
 196                 return 0;
 197
 198         type = get_type(expr);
 199         if (!type || type->type != SYM_ARRAY)
 200                 return 0;
 201
 202         ret = get_expression_value(type->array_size);
 203         /* Dynamically sized array are -1 in sparse */
 204         if (ret <= 0)
 205                 return 0;
 206         /* People put one element arrays on the end of structs */
 207         if (ret == 1)
 208                 return 0;
 209
 210         return ret;
 211 }
 212
 213 static int get_size_from_initializer(struct expression *expr)
 214 {
 215         if (expr->type != EXPR_SYMBOL || !expr->symbol->initializer)
 216                 return 0;
 217         if (expr->symbol->initializer == expr) /* int a = a; */
 218                 return 0;
 219         return get_initializer_size(expr->symbol->initializer);
 220 }
 221
 222 static int get_stored_size_bytes(struct expression *expr)
 223 {
 224         struct smatch_state *state;
 225
 226         state = get_state_expr(my_size_id, expr);
 227         if (!state)
 228                 return 0;
 229         return PTR_INT(state->data);
 230 }
 231
 232 static int get_stored_size_bytes_min(struct expression *expr)
 233 {
 234         struct sm_state *sm, *tmp;
 235         int min = 0;
 236
 237         sm = get_sm_state_expr(my_size_id, expr);
 238         if (!sm)
 239                 return 0;
 240         FOR_EACH_PTR(sm->possible, tmp) {
 241                 if (PTR_INT(tmp->state->data) <= 0)
 242                         continue;
 243                 if (PTR_INT(tmp->state->data) < min)
 244                         min = PTR_INT(tmp->state->data);
 245         } END_FOR_EACH_PTR(tmp);
 246
 247         return min;
 248 }
 249
 250 static int get_bytes_from_address(struct expression *expr)
 251 {
 252         struct symbol *type;
 253         int ret;
 254
 255         if (!option_spammy)
 256                 return 0;
 257         if (expr->type != EXPR_PREOP || expr->op != '&')
 258                 return 0;
 259         type = get_type(expr);
 260         if (!type)
 261                 return 0;
 262
 263         if (type->type == SYM_PTR)
 264                 type = get_base_type(type);
 265
 266         ret = bits_to_bytes(type->bit_size);
 267         if (ret == -1)
 268                 return 0;
 269         if (ret == 1)
 270                 return 0;  /* ignore char pointers */
 271
 272         return ret;
 273 }
 274
 275 static int get_size_from_strlen(struct expression *expr)
 276 {
 277         struct smatch_state *state;
 278         sval_t len;
 279
 280         state = get_state_expr(my_strlen_id, expr);
 281         if (!state || !state->data)
 282                 return 0;
 283         if (get_implied_max_sval((struct expression *)state->data, &len))
 284                 return len.value + 1; /* add one because strlen doesn't include the NULL */
 285         return 0;
 286 }
 287
 288 static struct expression *remove_addr_fluff(struct expression *expr)
 289 {
 290         struct expression *tmp;
 291         sval_t sval;
 292
 293         expr = strip_expr(expr);
 294
 295         /* remove '&' and '*' operations that cancel */
 296         while (expr->type == EXPR_PREOP && expr->op == '&') {
 297                 tmp = strip_expr(expr->unop);
 298                 if (tmp->type != EXPR_PREOP)
 299                         break;
 300                 if (tmp->op != '*')
 301                         break;
 302                 expr = strip_expr(tmp->unop);
 303         }
 304
 305         /* "foo + 0" is just "foo" */
 306         if (expr->type == EXPR_BINOP && expr->op == '+' &&
 307             get_value_sval(expr->right, &sval) && sval.value == 0)
 308                 return expr->left;
 309
 310         return expr;
 311 }
 312
 313 int get_array_size_bytes(struct expression *expr)
 314 {
 315         int size;
 316
 317         expr = remove_addr_fluff(expr);
 318         if (!expr)
 319                 return 0;
 320
 321         /* strcpy(foo, "BAR"); */
 322         if (expr->type == EXPR_STRING)
 323                 return expr->string->length;
 324
 325         /* buf[4] */
 326         size = get_real_array_size(expr);
 327         if (size)
 328                 return elements_to_bytes(expr, size);
 329
 330         /* buf = malloc(1024); */
 331         size = get_stored_size_bytes(expr);
 332         if (size)
 333                 return size;
 334
 335         /* char *foo = "BAR" */
 336         size = get_size_from_initializer(expr);
 337         if (size)
 338                 return elements_to_bytes(expr, size);
 339
 340         size = get_bytes_from_address(expr);
 341         if (size)
 342                 return size;
 343
 344         /* if (strlen(foo) > 4) */
 345         size = get_size_from_strlen(expr);
 346         if (size)
 347                 return size;
 348
 349         return size_from_db(expr);
 350 }
 351
 352 int get_array_size_bytes_min(struct expression *expr)
 353 {
 354         int size;
 355         int tmp;
 356
 357         size = get_array_size_bytes(expr);
 358
 359         tmp = get_stored_size_bytes_min(expr);
 360         if (size <= 0 || (tmp >= 1 && tmp < size))
 361                 size = tmp;
 362         return size;
 363 }
 364
 365 int get_array_size(struct expression *expr)
 366 {
 367         int bytes;
 368
 369         bytes = get_array_size_bytes(expr);
 370         return bytes_to_elements(expr, bytes);
 371 }
 372
 373 static void match_strlen_condition(struct expression *expr)
 374 {
 375         struct expression *left;
 376         struct expression *right;
 377         struct expression *str = NULL;
 378         int strlen_left = 0;
 379         int strlen_right = 0;
 380         sval_t sval;
 381         struct smatch_state *true_state = NULL;
 382         struct smatch_state *false_state = NULL;
 383
 384         if (expr->type != EXPR_COMPARE)
 385                 return;
 386         left = strip_expr(expr->left);
 387         right = strip_expr(expr->right);
 388
 389         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 390                 str = get_argument_from_call_expr(left->args, 0);
 391                 strlen_left = 1;
 392         }
 393         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 394                 str = get_argument_from_call_expr(right->args, 0);
 395                 strlen_right = 1;
 396         }
 397
 398         if (!strlen_left && !strlen_right)
 399                 return;
 400         if (strlen_left && strlen_right)
 401                 return;
 402
 403         if (strlen_left) {
 404                 if (!get_value_sval(right, &sval))
 405                         return;
 406         }
 407         if (strlen_right) {
 408                 if (!get_value_sval(left, &sval))
 409                         return;
 410         }
 411
 412         if (expr->op == SPECIAL_EQUAL) {
 413                 set_true_false_states_expr(my_size_id, str, alloc_state_num(sval.value + 1), NULL);
 414                 return;
 415         }
 416         if (expr->op == SPECIAL_NOTEQUAL) {
 417                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(sval.value + 1));
 418                 return;
 419         }
 420
 421         switch (expr->op) {
 422         case '<':
 423         case SPECIAL_UNSIGNED_LT:
 424                 if (strlen_left)
 425                         true_state = alloc_state_num(sval.value);
 426                 else
 427                         false_state = alloc_state_num(sval.value + 1);
 428                 break;
 429         case SPECIAL_LTE:
 430         case SPECIAL_UNSIGNED_LTE:
 431                 if (strlen_left)
 432                         true_state = alloc_state_num(sval.value + 1);
 433                 else
 434                         false_state = alloc_state_num(sval.value);
 435                 break;
 436         case SPECIAL_GTE:
 437         case SPECIAL_UNSIGNED_GTE:
 438                 if (strlen_left)
 439                         false_state = alloc_state_num(sval.value);
 440                 else
 441                         true_state = alloc_state_num(sval.value + 1);
 442                 break;
 443         case '>':
 444         case SPECIAL_UNSIGNED_GT:
 445                 if (strlen_left)
 446                         false_state = alloc_state_num(sval.value + 1);
 447                 else
 448                         true_state = alloc_state_num(sval.value);
 449                 break;
 450         }
 451         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 452 }
 453
 454 static struct expression *strip_ampersands(struct expression *expr)
 455 {
 456         struct symbol *type;
 457
 458         if (expr->type != EXPR_PREOP)
 459                 return expr;
 460         if (expr->op != '&')
 461                 return expr;
 462         type = get_type(expr->unop);
 463         if (!type || type->type != SYM_ARRAY)
 464                 return expr;
 465         return expr->unop;
 466 }
 467
 468 static void match_array_assignment(struct expression *expr)
 469 {
 470         struct expression *left;
 471         struct expression *right;
 472         int array_size;
 473
 474         if (expr->op != '=')
 475                 return;
 476         left = strip_expr(expr->left);
 477         right = strip_expr(expr->right);
 478         right = strip_ampersands(right);
 479         array_size = get_array_size_bytes(right);
 480         if (array_size)
 481                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 482 }
 483
 484 static void info_record_alloction(struct expression *buffer, struct expression *size)
 485 {
 486         char *name;
 487         sval_t sval;
 488
 489         if (!option_info)
 490                 return;
 491
 492         name = get_member_name(buffer);
 493         if (!name && is_static(buffer))
 494                 name = get_variable_from_expr(buffer, NULL);
 495         if (!name)
 496                 return;
 497         if (get_implied_value_sval(size, &sval))
 498                 sm_msg("info: '%s' allocated_buf_size %s", name, sval_to_str(sval));
 499         else
 500                 sm_msg("info: '%s' allocated_buf_size -1", name);
 501         free_string(name);
 502 }
 503
 504 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 505 {
 506         int size_arg = PTR_INT(_size_arg);
 507         struct expression *right;
 508         struct expression *arg;
 509         sval_t bytes;
 510
 511         right = strip_expr(expr->right);
 512         arg = get_argument_from_call_expr(right->args, size_arg);
 513
 514         info_record_alloction(expr->left, arg);
 515
 516         if (!get_implied_value_sval(arg, &bytes))
 517                 return;
 518         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes.value));
 519 }
 520
 521 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 522 {
 523         struct expression *right;
 524         struct expression *arg;
 525         sval_t elements;
 526         sval_t size;
 527
 528         right = strip_expr(expr->right);
 529         arg = get_argument_from_call_expr(right->args, 0);
 530         if (!get_implied_value_sval(arg, &elements))
 531                 return;
 532         arg = get_argument_from_call_expr(right->args, 1);
 533         if (!get_implied_value_sval(arg, &size))
 534                 return;
 535         set_state_expr(my_size_id, expr->left, alloc_state_num(elements.value * size.value));
 536 }
 537
 538 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 539 {
 540         struct expression *right;
 541         struct expression *str;
 542         struct expression *len_expr;
 543         char *len_name;
 544         struct smatch_state *state;
 545
 546         right = strip_expr(expr->right);
 547         str = get_argument_from_call_expr(right->args, 0);
 548         len_expr = strip_expr(expr->left);
 549
 550         len_name = get_variable_from_expr(len_expr, NULL);
 551         if (!len_name)
 552                 return;
 553
 554         state = __alloc_smatch_state(0);
 555         state->name = len_name;
 556         state->data = len_expr;
 557         set_state_expr(my_strlen_id, str, state);
 558 }
 559
 560 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 561 {
 562         struct limiter *limiter = (struct limiter *)_limiter;
 563         struct expression *dest;
 564         struct expression *size_expr;
 565         sval_t size;
 566
 567         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 568         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 569         if (!get_implied_max_sval(size_expr, &size))
 570                 return;
 571         set_state_expr(my_size_id, dest, alloc_state_num(size.value));
 572 }
 573
 574 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 575 {
 576         struct expression fake_assign;
 577
 578         fake_assign.op = '=';
 579         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 580         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 581         match_array_assignment(&fake_assign);
 582 }
 583
 584 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 585 {
 586         struct expression *fn_expr;
 587         struct expression *size_expr;
 588         sval_t size;
 589
 590         fn_expr = strip_expr(expr->right);
 591         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 592         if (!get_implied_max_sval(size_expr, &size))
 593                 return;
 594
 595         /* It's easy to forget space for the NUL char */
 596         size.value++;
 597         set_state_expr(my_size_id, expr->left, alloc_state_num(size.value));
 598 }
 599
 600 static void match_call(struct expression *expr)
 601 {
 602         char *name;
 603         struct expression *arg;
 604         int bytes;
 605         int i;
 606
 607         name = get_fnptr_name(expr->fn);
 608         if (!name)
 609                 return;
 610
 611         i = 0;
 612         FOR_EACH_PTR(expr->args, arg) {
 613                 bytes = get_array_size_bytes(arg);
 614                 if (bytes > 1)
 615                         sm_msg("info: passes_buffer '%s' %d '$$' %d %s",
 616                                 name, i, bytes,
 617                                 is_static(expr->fn) ? "static" : "global");
 618                 i++;
 619         } END_FOR_EACH_PTR(arg);
 620
 621         free_string(name);
 622 }
 623
 624 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 625 {
 626         if (state == &merged)
 627                 return;
 628         sm_msg("info: passes_buffer '%s' %d '%s' %s %s", fn, param, printed_name, state->name, global_static);
 629 }
 630
 631 static void match_func_end(struct symbol *sym)
 632 {
 633         memset(params_set, 0, sizeof(params_set));
 634 }
 635
 636 void register_buf_size(int id)
 637 {
 638         my_size_id = id;
 639
 640         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 641         add_db_return_states_callback(BUF_SIZE, &db_returns_buf_size);
 642
 643         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 644         add_function_assign_hook("calloc", &match_calloc, NULL);
 645         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 646         if (option_project == PROJ_KERNEL) {
 647                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 648                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 649                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 650                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 651                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 652                 add_function_assign_hook("kmalloc_array", &match_calloc, NULL);
 653                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 654                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 655                 add_function_assign_hook("sock_kmalloc", &match_alloc, INT_PTR(1));
 656                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 657                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 658         }
 659         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 660         add_hook(&match_strlen_condition, CONDITION_HOOK);
 661         add_function_assign_hook("strlen", &match_strlen, NULL);
 662
 663         add_function_assign_hook("strndup", match_strndup, NULL);
 664         if (option_project == PROJ_KERNEL)
 665                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 666
 667         add_hook(&match_func_end, END_FUNC_HOOK);
 668         add_modification_hook(my_size_id, &set_undefined);
 669
 670         add_merge_hook(my_size_id, &merge_func);
 671 }
 672
 673 void register_strlen(int id)
 674 {
 675         my_strlen_id = id;
 676         add_modification_hook(my_strlen_id, &set_undefined);
 677         add_merge_hook(my_strlen_id, &merge_func);
 678 }
 679
 680 void register_buf_size_late(int id)
 681 {
 682         add_function_hook("strlcpy", &match_limited, &b0_l2);
 683         add_function_hook("strlcat", &match_limited, &b0_l2);
 684         add_function_hook("memscan", &match_limited, &b0_l2);
 685
 686         add_function_hook("strcpy", &match_strcpy, NULL);
 687
 688         if (option_info) {
 689                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 690                 add_member_info_callback(my_size_id, struct_member_callback);
 691         }
 692 }