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 = expr_to_var(expr);
 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(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         sval_t sval;
 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         if (!get_implied_value(type->array_size, &sval))
 203                 return 0;
 204
 205         /* People put one element arrays on the end of structs */
 206         if (sval.value == 1)
 207                 return 0;
 208
 209         return sval.value;
 210 }
 211
 212 static int get_size_from_initializer(struct expression *expr)
 213 {
 214         if (expr->type != EXPR_SYMBOL || !expr->symbol->initializer)
 215                 return 0;
 216         if (expr->symbol->initializer == expr) /* int a = a; */
 217                 return 0;
 218         return get_initializer_size(expr->symbol->initializer);
 219 }
 220
 221 static int get_stored_size_bytes(struct expression *expr)
 222 {
 223         struct smatch_state *state;
 224
 225         state = get_state_expr(my_size_id, expr);
 226         if (!state)
 227                 return 0;
 228         return PTR_INT(state->data);
 229 }
 230
 231 static int get_stored_size_bytes_min(struct expression *expr)
 232 {
 233         struct sm_state *sm, *tmp;
 234         int min = 0;
 235
 236         sm = get_sm_state_expr(my_size_id, expr);
 237         if (!sm)
 238                 return 0;
 239         FOR_EACH_PTR(sm->possible, tmp) {
 240                 if (PTR_INT(tmp->state->data) <= 0)
 241                         continue;
 242                 if (PTR_INT(tmp->state->data) < min)
 243                         min = PTR_INT(tmp->state->data);
 244         } END_FOR_EACH_PTR(tmp);
 245
 246         return min;
 247 }
 248
 249 static int get_bytes_from_address(struct expression *expr)
 250 {
 251         struct symbol *type;
 252         int ret;
 253
 254         if (!option_spammy)
 255                 return 0;
 256         if (expr->type != EXPR_PREOP || expr->op != '&')
 257                 return 0;
 258         type = get_type(expr);
 259         if (!type)
 260                 return 0;
 261
 262         if (type->type == SYM_PTR)
 263                 type = get_base_type(type);
 264
 265         ret = bits_to_bytes(type->bit_size);
 266         if (ret == -1)
 267                 return 0;
 268         if (ret == 1)
 269                 return 0;  /* ignore char pointers */
 270
 271         return ret;
 272 }
 273
 274 static int get_size_from_strlen(struct expression *expr)
 275 {
 276         struct smatch_state *state;
 277         sval_t len;
 278
 279         state = get_state_expr(my_strlen_id, expr);
 280         if (!state || !state->data)
 281                 return 0;
 282         if (get_implied_max((struct expression *)state->data, &len))
 283                 return len.value + 1; /* add one because strlen doesn't include the NULL */
 284         return 0;
 285 }
 286
 287 static struct expression *remove_addr_fluff(struct expression *expr)
 288 {
 289         struct expression *tmp;
 290         sval_t sval;
 291
 292         expr = strip_expr(expr);
 293
 294         /* remove '&' and '*' operations that cancel */
 295         while (expr->type == EXPR_PREOP && expr->op == '&') {
 296                 tmp = strip_expr(expr->unop);
 297                 if (tmp->type != EXPR_PREOP)
 298                         break;
 299                 if (tmp->op != '*')
 300                         break;
 301                 expr = strip_expr(tmp->unop);
 302         }
 303
 304         /* "foo + 0" is just "foo" */
 305         if (expr->type == EXPR_BINOP && expr->op == '+' &&
 306             get_value(expr->right, &sval) && sval.value == 0)
 307                 return expr->left;
 308
 309         return expr;
 310 }
 311
 312 int get_array_size_bytes(struct expression *expr)
 313 {
 314         int size;
 315
 316         expr = remove_addr_fluff(expr);
 317         if (!expr)
 318                 return 0;
 319
 320         /* strcpy(foo, "BAR"); */
 321         if (expr->type == EXPR_STRING)
 322                 return expr->string->length;
 323
 324         /* buf[4] */
 325         size = get_real_array_size(expr);
 326         if (size)
 327                 return elements_to_bytes(expr, size);
 328
 329         /* buf = malloc(1024); */
 330         size = get_stored_size_bytes(expr);
 331         if (size)
 332                 return size;
 333
 334         /* char *foo = "BAR" */
 335         size = get_size_from_initializer(expr);
 336         if (size)
 337                 return elements_to_bytes(expr, size);
 338
 339         size = get_bytes_from_address(expr);
 340         if (size)
 341                 return size;
 342
 343         /* if (strlen(foo) > 4) */
 344         size = get_size_from_strlen(expr);
 345         if (size)
 346                 return size;
 347
 348         return size_from_db(expr);
 349 }
 350
 351 int get_array_size_bytes_min(struct expression *expr)
 352 {
 353         int size;
 354         int tmp;
 355
 356         size = get_array_size_bytes(expr);
 357
 358         tmp = get_stored_size_bytes_min(expr);
 359         if (size <= 0 || (tmp >= 1 && tmp < size))
 360                 size = tmp;
 361         return size;
 362 }
 363
 364 int get_array_size(struct expression *expr)
 365 {
 366         int bytes;
 367
 368         bytes = get_array_size_bytes(expr);
 369         return bytes_to_elements(expr, bytes);
 370 }
 371
 372 static void match_strlen_condition(struct expression *expr)
 373 {
 374         struct expression *left;
 375         struct expression *right;
 376         struct expression *str = NULL;
 377         int strlen_left = 0;
 378         int strlen_right = 0;
 379         sval_t sval;
 380         struct smatch_state *true_state = NULL;
 381         struct smatch_state *false_state = NULL;
 382
 383         if (expr->type != EXPR_COMPARE)
 384                 return;
 385         left = strip_expr(expr->left);
 386         right = strip_expr(expr->right);
 387
 388         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 389                 str = get_argument_from_call_expr(left->args, 0);
 390                 strlen_left = 1;
 391         }
 392         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 393                 str = get_argument_from_call_expr(right->args, 0);
 394                 strlen_right = 1;
 395         }
 396
 397         if (!strlen_left && !strlen_right)
 398                 return;
 399         if (strlen_left && strlen_right)
 400                 return;
 401
 402         if (strlen_left) {
 403                 if (!get_value(right, &sval))
 404                         return;
 405         }
 406         if (strlen_right) {
 407                 if (!get_value(left, &sval))
 408                         return;
 409         }
 410
 411         if (expr->op == SPECIAL_EQUAL) {
 412                 set_true_false_states_expr(my_size_id, str, alloc_state_num(sval.value + 1), NULL);
 413                 return;
 414         }
 415         if (expr->op == SPECIAL_NOTEQUAL) {
 416                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(sval.value + 1));
 417                 return;
 418         }
 419
 420         switch (expr->op) {
 421         case '<':
 422         case SPECIAL_UNSIGNED_LT:
 423                 if (strlen_left)
 424                         true_state = alloc_state_num(sval.value);
 425                 else
 426                         false_state = alloc_state_num(sval.value + 1);
 427                 break;
 428         case SPECIAL_LTE:
 429         case SPECIAL_UNSIGNED_LTE:
 430                 if (strlen_left)
 431                         true_state = alloc_state_num(sval.value + 1);
 432                 else
 433                         false_state = alloc_state_num(sval.value);
 434                 break;
 435         case SPECIAL_GTE:
 436         case SPECIAL_UNSIGNED_GTE:
 437                 if (strlen_left)
 438                         false_state = alloc_state_num(sval.value);
 439                 else
 440                         true_state = alloc_state_num(sval.value + 1);
 441                 break;
 442         case '>':
 443         case SPECIAL_UNSIGNED_GT:
 444                 if (strlen_left)
 445                         false_state = alloc_state_num(sval.value + 1);
 446                 else
 447                         true_state = alloc_state_num(sval.value);
 448                 break;
 449         }
 450         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 451 }
 452
 453 static struct expression *strip_ampersands(struct expression *expr)
 454 {
 455         struct symbol *type;
 456
 457         if (expr->type != EXPR_PREOP)
 458                 return expr;
 459         if (expr->op != '&')
 460                 return expr;
 461         type = get_type(expr->unop);
 462         if (!type || type->type != SYM_ARRAY)
 463                 return expr;
 464         return expr->unop;
 465 }
 466
 467 static void match_array_assignment(struct expression *expr)
 468 {
 469         struct expression *left;
 470         struct expression *right;
 471         int array_size;
 472
 473         if (expr->op != '=')
 474                 return;
 475         left = strip_expr(expr->left);
 476         right = strip_expr(expr->right);
 477         right = strip_ampersands(right);
 478         array_size = get_array_size_bytes(right);
 479         if (array_size)
 480                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 481 }
 482
 483 static void info_record_alloction(struct expression *buffer, struct expression *size)
 484 {
 485         char *name;
 486         sval_t sval;
 487
 488         if (!option_info)
 489                 return;
 490
 491         name = get_member_name(buffer);
 492         if (!name && is_static(buffer))
 493                 name = expr_to_var(buffer);
 494         if (!name)
 495                 return;
 496         if (get_implied_value(size, &sval))
 497                 sm_msg("info: '%s' allocated_buf_size %s", name, sval_to_str(sval));
 498         else
 499                 sm_msg("info: '%s' allocated_buf_size -1", name);
 500         free_string(name);
 501 }
 502
 503 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 504 {
 505         int size_arg = PTR_INT(_size_arg);
 506         struct expression *right;
 507         struct expression *arg;
 508         sval_t bytes;
 509
 510         right = strip_expr(expr->right);
 511         arg = get_argument_from_call_expr(right->args, size_arg);
 512
 513         info_record_alloction(expr->left, arg);
 514
 515         if (!get_implied_value(arg, &bytes))
 516                 return;
 517         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes.value));
 518 }
 519
 520 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 521 {
 522         struct expression *right;
 523         struct expression *arg;
 524         sval_t elements;
 525         sval_t size;
 526
 527         right = strip_expr(expr->right);
 528         arg = get_argument_from_call_expr(right->args, 0);
 529         if (!get_implied_value(arg, &elements))
 530                 return;
 531         arg = get_argument_from_call_expr(right->args, 1);
 532         if (!get_implied_value(arg, &size))
 533                 return;
 534         set_state_expr(my_size_id, expr->left, alloc_state_num(elements.value * size.value));
 535 }
 536
 537 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 538 {
 539         struct expression *right;
 540         struct expression *str;
 541         struct expression *len_expr;
 542         char *len_name;
 543         struct smatch_state *state;
 544
 545         right = strip_expr(expr->right);
 546         str = get_argument_from_call_expr(right->args, 0);
 547         len_expr = strip_expr(expr->left);
 548
 549         len_name = expr_to_var(len_expr);
 550         if (!len_name)
 551                 return;
 552
 553         state = __alloc_smatch_state(0);
 554         state->name = len_name;
 555         state->data = len_expr;
 556         set_state_expr(my_strlen_id, str, state);
 557 }
 558
 559 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 560 {
 561         struct limiter *limiter = (struct limiter *)_limiter;
 562         struct expression *dest;
 563         struct expression *size_expr;
 564         sval_t size;
 565
 566         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 567         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 568         if (!get_implied_max(size_expr, &size))
 569                 return;
 570         set_state_expr(my_size_id, dest, alloc_state_num(size.value));
 571 }
 572
 573 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 574 {
 575         struct expression fake_assign;
 576
 577         fake_assign.op = '=';
 578         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 579         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 580         match_array_assignment(&fake_assign);
 581 }
 582
 583 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 584 {
 585         struct expression *fn_expr;
 586         struct expression *size_expr;
 587         sval_t size;
 588
 589         fn_expr = strip_expr(expr->right);
 590         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 591         if (!get_implied_max(size_expr, &size))
 592                 return;
 593
 594         /* It's easy to forget space for the NUL char */
 595         size.value++;
 596         set_state_expr(my_size_id, expr->left, alloc_state_num(size.value));
 597 }
 598
 599 static void match_call(struct expression *expr)
 600 {
 601         char *name;
 602         struct expression *arg;
 603         int bytes;
 604         int i;
 605
 606         name = get_fnptr_name(expr->fn);
 607         if (!name)
 608                 return;
 609
 610         i = 0;
 611         FOR_EACH_PTR(expr->args, arg) {
 612                 bytes = get_array_size_bytes(arg);
 613                 if (bytes > 1)
 614                         sm_msg("info: passes_buffer '%s' %d '$$' %d %s",
 615                                 name, i, bytes,
 616                                 is_static(expr->fn) ? "static" : "global");
 617                 i++;
 618         } END_FOR_EACH_PTR(arg);
 619
 620         free_string(name);
 621 }
 622
 623 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 624 {
 625         if (state == &merged)
 626                 return;
 627         sm_msg("info: passes_buffer '%s' %d '%s' %s %s", fn, param, printed_name, state->name, global_static);
 628 }
 629
 630 static void match_func_end(struct symbol *sym)
 631 {
 632         memset(params_set, 0, sizeof(params_set));
 633 }
 634
 635 void register_buf_size(int id)
 636 {
 637         my_size_id = id;
 638
 639         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 640         add_db_return_states_callback(BUF_SIZE, &db_returns_buf_size);
 641
 642         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 643         add_function_assign_hook("calloc", &match_calloc, NULL);
 644         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 645         if (option_project == PROJ_KERNEL) {
 646                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 647                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 648                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 649                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 650                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 651                 add_function_assign_hook("kmalloc_array", &match_calloc, NULL);
 652                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 653                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 654                 add_function_assign_hook("sock_kmalloc", &match_alloc, INT_PTR(1));
 655                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 656                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 657         }
 658         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 659         add_hook(&match_strlen_condition, CONDITION_HOOK);
 660         add_function_assign_hook("strlen", &match_strlen, NULL);
 661
 662         add_function_assign_hook("strndup", match_strndup, NULL);
 663         if (option_project == PROJ_KERNEL)
 664                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 665
 666         add_hook(&match_func_end, END_FUNC_HOOK);
 667         add_modification_hook(my_size_id, &set_undefined);
 668
 669         add_merge_hook(my_size_id, &merge_func);
 670 }
 671
 672 void register_strlen(int id)
 673 {
 674         my_strlen_id = id;
 675         add_modification_hook(my_strlen_id, &set_undefined);
 676         add_merge_hook(my_strlen_id, &merge_func);
 677 }
 678
 679 void register_buf_size_late(int id)
 680 {
 681         add_function_hook("strlcpy", &match_limited, &b0_l2);
 682         add_function_hook("strlcat", &match_limited, &b0_l2);
 683         add_function_hook("memscan", &match_limited, &b0_l2);
 684
 685         add_function_hook("strcpy", &match_strcpy, NULL);
 686
 687         if (option_info) {
 688                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 689                 add_member_info_callback(my_size_id, struct_member_callback);
 690         }
 691 }