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 int get_real_array_size(struct expression *expr)
 177 {
 178         struct symbol *type;
 179         int ret;
 180
 181         if (expr->type == EXPR_BINOP) /* array elements foo[5] */
 182                 return 0;
 183
 184         type = get_type(expr);
 185         if (!type || type->type != SYM_ARRAY)
 186                 return 0;
 187
 188         ret = get_expression_value(type->array_size);
 189         /* Dynamically sized array are -1 in sparse */
 190         if (ret <= 0)
 191                 return 0;
 192         /* People put one element arrays on the end of structs */
 193         if (ret == 1)
 194                 return 0;
 195
 196         return ret;
 197 }
 198
 199 static int get_size_from_initializer(struct expression *expr)
 200 {
 201         if (expr->type != EXPR_SYMBOL || !expr->symbol->initializer)
 202                 return 0;
 203         if (expr->symbol->initializer == expr) /* int a = a; */
 204                 return 0;
 205         return get_initializer_size(expr->symbol->initializer);
 206 }
 207
 208 static int get_stored_size_bytes(struct expression *expr)
 209 {
 210         struct smatch_state *state;
 211
 212         state = get_state_expr(my_size_id, expr);
 213         if (!state)
 214                 return 0;
 215         return PTR_INT(state->data);
 216 }
 217
 218 static int get_stored_size_bytes_min(struct expression *expr)
 219 {
 220         struct sm_state *sm, *tmp;
 221         int min = 0;
 222
 223         sm = get_sm_state_expr(my_size_id, expr);
 224         if (!sm)
 225                 return 0;
 226         FOR_EACH_PTR(sm->possible, tmp) {
 227                 if (PTR_INT(tmp->state->data) <= 0)
 228                         continue;
 229                 if (PTR_INT(tmp->state->data) < min)
 230                         min = PTR_INT(tmp->state->data);
 231         } END_FOR_EACH_PTR(tmp);
 232
 233         return min;
 234 }
 235
 236 static int get_bytes_from_address(struct expression *expr)
 237 {
 238         struct symbol *type;
 239         int ret;
 240
 241         if (!option_spammy)
 242                 return 0;
 243         if (expr->type != EXPR_PREOP || expr->op != '&')
 244                 return 0;
 245         type = get_type(expr);
 246         if (!type)
 247                 return 0;
 248
 249         if (type->type == SYM_PTR)
 250                 type = get_base_type(type);
 251
 252         ret = bits_to_bytes(type->bit_size);
 253         if (ret == -1)
 254                 return 0;
 255         if (ret == 1)
 256                 return 0;  /* ignore char pointers */
 257
 258         return ret;
 259 }
 260
 261 static int get_size_from_strlen(struct expression *expr)
 262 {
 263         struct smatch_state *state;
 264         long long len;
 265
 266         state = get_state_expr(my_strlen_id, expr);
 267         if (!state || !state->data)
 268                 return 0;
 269         if (get_implied_max((struct expression *)state->data, &len))
 270                 return len + 1; /* add one because strlen doesn't include the NULL */
 271         return 0;
 272 }
 273
 274 static struct expression *remove_addr_fluff(struct expression *expr)
 275 {
 276         struct expression *tmp;
 277         long long val;
 278
 279         expr = strip_expr(expr);
 280
 281         /* remove '&' and '*' operations that cancel */
 282         while (expr->type == EXPR_PREOP && expr->op == '&') {
 283                 tmp = strip_expr(expr->unop);
 284                 if (tmp->type != EXPR_PREOP)
 285                         break;
 286                 if (tmp->op != '*')
 287                         break;
 288                 expr = strip_expr(tmp->unop);
 289         }
 290
 291         /* "foo + 0" is just "foo" */
 292         if (expr->type == EXPR_BINOP && expr->op == '+' &&
 293             get_value(expr->right, &val) && val == 0)
 294                 return expr->left;
 295
 296         return expr;
 297 }
 298
 299 int get_array_size_bytes(struct expression *expr)
 300 {
 301         int size;
 302
 303         expr = remove_addr_fluff(expr);
 304         if (!expr)
 305                 return 0;
 306
 307         /* strcpy(foo, "BAR"); */
 308         if (expr->type == EXPR_STRING)
 309                 return expr->string->length;
 310
 311         /* buf[4] */
 312         size = get_real_array_size(expr);
 313         if (size)
 314                 return elements_to_bytes(expr, size);
 315
 316         /* buf = malloc(1024); */
 317         size = get_stored_size_bytes(expr);
 318         if (size)
 319                 return size;
 320
 321         /* char *foo = "BAR" */
 322         size = get_size_from_initializer(expr);
 323         if (size)
 324                 return elements_to_bytes(expr, size);
 325
 326         size = get_bytes_from_address(expr);
 327         if (size)
 328                 return size;
 329
 330         /* if (strlen(foo) > 4) */
 331         size = get_size_from_strlen(expr);
 332         if (size)
 333                 return size;
 334
 335         return size_from_db(expr);
 336 }
 337
 338 int get_array_size_bytes_min(struct expression *expr)
 339 {
 340         int size;
 341         int tmp;
 342
 343         size = get_array_size_bytes(expr);
 344
 345         tmp = get_stored_size_bytes_min(expr);
 346         if (size <= 0 || (tmp >= 1 && tmp < size))
 347                 size = tmp;
 348         return size;
 349 }
 350
 351 int get_array_size(struct expression *expr)
 352 {
 353         int bytes;
 354
 355         bytes = get_array_size_bytes(expr);
 356         return bytes_to_elements(expr, bytes);
 357 }
 358
 359 static void match_strlen_condition(struct expression *expr)
 360 {
 361         struct expression *left;
 362         struct expression *right;
 363         struct expression *str = NULL;
 364         int strlen_left = 0;
 365         int strlen_right = 0;
 366         long long val;
 367         struct smatch_state *true_state = NULL;
 368         struct smatch_state *false_state = NULL;
 369
 370         if (expr->type != EXPR_COMPARE)
 371                 return;
 372         left = strip_expr(expr->left);
 373         right = strip_expr(expr->right);
 374
 375         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 376                 str = get_argument_from_call_expr(left->args, 0);
 377                 strlen_left = 1;
 378         }
 379         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 380                 str = get_argument_from_call_expr(right->args, 0);
 381                 strlen_right = 1;
 382         }
 383
 384         if (!strlen_left && !strlen_right)
 385                 return;
 386         if (strlen_left && strlen_right)
 387                 return;
 388
 389         if (strlen_left) {
 390                 if (!get_value(right, &val))
 391                         return;
 392         }
 393         if (strlen_right) {
 394                 if (!get_value(left, &val))
 395                         return;
 396         }
 397
 398         if (expr->op == SPECIAL_EQUAL) {
 399                 set_true_false_states_expr(my_size_id, str, alloc_state_num(val + 1), NULL);
 400                 return;
 401         }
 402         if (expr->op == SPECIAL_NOTEQUAL) {
 403                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(val + 1));
 404                 return;
 405         }
 406
 407         switch (expr->op) {
 408         case '<':
 409         case SPECIAL_UNSIGNED_LT:
 410                 if (strlen_left)
 411                         true_state = alloc_state_num(val);
 412                 else
 413                         false_state = alloc_state_num(val + 1);
 414                 break;
 415         case SPECIAL_LTE:
 416         case SPECIAL_UNSIGNED_LTE:
 417                 if (strlen_left)
 418                         true_state = alloc_state_num(val + 1);
 419                 else
 420                         false_state = alloc_state_num(val);
 421                 break;
 422         case SPECIAL_GTE:
 423         case SPECIAL_UNSIGNED_GTE:
 424                 if (strlen_left)
 425                         false_state = alloc_state_num(val);
 426                 else
 427                         true_state = alloc_state_num(val + 1);
 428                 break;
 429         case '>':
 430         case SPECIAL_UNSIGNED_GT:
 431                 if (strlen_left)
 432                         false_state = alloc_state_num(val + 1);
 433                 else
 434                         true_state = alloc_state_num(val);
 435                 break;
 436         }
 437         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 438 }
 439
 440 static struct expression *strip_ampersands(struct expression *expr)
 441 {
 442         struct symbol *type;
 443
 444         if (expr->type != EXPR_PREOP)
 445                 return expr;
 446         if (expr->op != '&')
 447                 return expr;
 448         type = get_type(expr->unop);
 449         if (!type || type->type != SYM_ARRAY)
 450                 return expr;
 451         return expr->unop;
 452 }
 453
 454 static void match_array_assignment(struct expression *expr)
 455 {
 456         struct expression *left;
 457         struct expression *right;
 458         int array_size;
 459
 460         if (expr->op != '=')
 461                 return;
 462         left = strip_expr(expr->left);
 463         right = strip_expr(expr->right);
 464         right = strip_ampersands(right);
 465         array_size = get_array_size_bytes(right);
 466         if (array_size)
 467                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 468 }
 469
 470 static void info_record_alloction(struct expression *buffer, struct expression *size)
 471 {
 472         char *name;
 473         long long val;
 474
 475         if (!option_info)
 476                 return;
 477
 478         name = get_member_name(buffer);
 479         if (!name && is_static(buffer))
 480                 name = get_variable_from_expr(buffer, NULL);
 481         if (!name)
 482                 return;
 483         if (!get_implied_value(size, &val))
 484                 val = -1;
 485         sm_msg("info: '%s' allocated_buf_size %lld", name, val);
 486         free_string(name);
 487 }
 488
 489 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 490 {
 491         int size_arg = PTR_INT(_size_arg);
 492         struct expression *right;
 493         struct expression *arg;
 494         long long bytes;
 495
 496         right = strip_expr(expr->right);
 497         arg = get_argument_from_call_expr(right->args, size_arg);
 498
 499         info_record_alloction(expr->left, arg);
 500
 501         if (!get_implied_value(arg, &bytes))
 502                 return;
 503         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes));
 504 }
 505
 506 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 507 {
 508         struct expression *right;
 509         struct expression *arg;
 510         long long elements;
 511         long long size;
 512
 513         right = strip_expr(expr->right);
 514         arg = get_argument_from_call_expr(right->args, 0);
 515         if (!get_implied_value(arg, &elements))
 516                 return;
 517         arg = get_argument_from_call_expr(right->args, 1);
 518         if (!get_implied_value(arg, &size))
 519                 return;
 520         set_state_expr(my_size_id, expr->left, alloc_state_num(elements * size));
 521 }
 522
 523 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 524 {
 525         struct expression *right;
 526         struct expression *str;
 527         struct expression *len_expr;
 528         char *len_name;
 529         struct smatch_state *state;
 530
 531         right = strip_expr(expr->right);
 532         str = get_argument_from_call_expr(right->args, 0);
 533         len_expr = strip_expr(expr->left);
 534
 535         len_name = get_variable_from_expr(len_expr, NULL);
 536         if (!len_name)
 537                 return;
 538
 539         state = __alloc_smatch_state(0);
 540         state->name = len_name;
 541         state->data = len_expr;
 542         set_state_expr(my_strlen_id, str, state);
 543 }
 544
 545 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 546 {
 547         struct limiter *limiter = (struct limiter *)_limiter;
 548         struct expression *dest;
 549         struct expression *size_expr;
 550         long long size;
 551
 552         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 553         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 554         if (!get_implied_max(size_expr, &size))
 555                 return;
 556         set_state_expr(my_size_id, dest, alloc_state_num(size));
 557 }
 558
 559 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 560 {
 561         struct expression fake_assign;
 562
 563         fake_assign.op = '=';
 564         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 565         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 566         match_array_assignment(&fake_assign);
 567 }
 568
 569 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 570 {
 571         struct expression *fn_expr;
 572         struct expression *size_expr;
 573         long long size;
 574
 575         fn_expr = strip_expr(expr->right);
 576         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 577         if (!get_implied_max(size_expr, &size))
 578                 return;
 579
 580         /* It's easy to forget space for the NUL char */
 581         size++;
 582         set_state_expr(my_size_id, expr->left, alloc_state_num(size));
 583 }
 584
 585 static void match_call(struct expression *expr)
 586 {
 587         char *name;
 588         struct expression *arg;
 589         int bytes;
 590         int i;
 591
 592         name = get_fnptr_name(expr->fn);
 593         if (!name)
 594                 return;
 595
 596         i = 0;
 597         FOR_EACH_PTR(expr->args, arg) {
 598                 bytes = get_array_size_bytes(arg);
 599                 if (bytes > 1)
 600                         sm_msg("info: passes_buffer '%s' %d '$$' %d %s",
 601                                 name, i, bytes,
 602                                 is_static(expr->fn) ? "static" : "global");
 603                 i++;
 604         } END_FOR_EACH_PTR(arg);
 605
 606         free_string(name);
 607 }
 608
 609 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 610 {
 611         if (state == &merged)
 612                 return;
 613         sm_msg("info: passes_buffer '%s' %d '%s' %s %s", fn, param, printed_name, state->name, global_static);
 614 }
 615
 616 static void match_func_end(struct symbol *sym)
 617 {
 618         memset(params_set, 0, sizeof(params_set));
 619 }
 620
 621 void register_buf_size(int id)
 622 {
 623         my_size_id = id;
 624
 625         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 626
 627         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 628         add_function_assign_hook("calloc", &match_calloc, NULL);
 629         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 630         if (option_project == PROJ_KERNEL) {
 631                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 632                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 633                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 634                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 635                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 636                 add_function_assign_hook("kmalloc_array", &match_calloc, NULL);
 637                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 638                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 639                 add_function_assign_hook("sock_kmalloc", &match_alloc, INT_PTR(1));
 640                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 641                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 642         }
 643         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 644         add_hook(&match_strlen_condition, CONDITION_HOOK);
 645         add_function_assign_hook("strlen", &match_strlen, NULL);
 646
 647         add_function_assign_hook("strndup", match_strndup, NULL);
 648         if (option_project == PROJ_KERNEL)
 649                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 650
 651         add_hook(&match_func_end, END_FUNC_HOOK);
 652         add_modification_hook(my_size_id, &set_undefined);
 653
 654         add_merge_hook(my_size_id, &merge_func);
 655 }
 656
 657 void register_strlen(int id)
 658 {
 659         my_strlen_id = id;
 660         add_modification_hook(my_strlen_id, &set_undefined);
 661         add_merge_hook(my_strlen_id, &merge_func);
 662 }
 663
 664 void register_buf_size_late(int id)
 665 {
 666         add_function_hook("strlcpy", &match_limited, &b0_l2);
 667         add_function_hook("strlcat", &match_limited, &b0_l2);
 668         add_function_hook("memscan", &match_limited, &b0_l2);
 669
 670         add_function_hook("strcpy", &match_strcpy, NULL);
 671
 672         if (option_info) {
 673                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 674                 add_member_info_callback(my_size_id, struct_member_callback);
 675         }
 676 }