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         db_size = atoi(argv[0]);
 128         return 0;
 129 }
 130
 131 static int size_from_db(struct expression *expr)
 132 {
 133         char *name;
 134
 135         if (!option_spammy)
 136                 return 0;
 137
 138         name = get_member_name(expr);
 139         if (!name)
 140                 return 0;
 141
 142         db_size = 0;
 143         run_sql(db_size_callback, "select size from type_size where type = '%s'",
 144                         name);
 145         return db_size;
 146 }
 147
 148 static int get_real_array_size(struct expression *expr)
 149 {
 150         struct symbol *type;
 151         int ret;
 152
 153         if (expr->type == EXPR_BINOP) /* array elements foo[5] */
 154                 return 0;
 155
 156         type = get_type(expr);
 157         if (!type || type->type != SYM_ARRAY)
 158                 return 0;
 159
 160         ret = get_expression_value(type->array_size);
 161         /* Dynamically sized array are -1 in sparse */
 162         if (ret <= 0)
 163                 return 0;
 164         /* People put one element arrays on the end of structs */
 165         if (ret == 1)
 166                 return 0;
 167
 168         return ret;
 169 }
 170
 171 static int get_size_from_initializer(struct expression *expr)
 172 {
 173         if (expr->type != EXPR_SYMBOL || !expr->symbol->initializer)
 174                 return 0;
 175         if (expr->symbol->initializer == expr) /* int a = a; */
 176                 return 0;
 177         return get_initializer_size(expr->symbol->initializer);
 178 }
 179
 180 static int get_stored_size_bytes(struct expression *expr)
 181 {
 182         struct smatch_state *state;
 183
 184         state = get_state_expr(my_size_id, expr);
 185         if (!state)
 186                 return 0;
 187         return PTR_INT(state->data);
 188 }
 189
 190 static int get_bytes_from_address(struct expression *expr)
 191 {
 192         struct symbol *type;
 193         int ret;
 194
 195         if (!option_spammy)
 196                 return 0;
 197         if (expr->type != EXPR_PREOP || expr->op != '&')
 198                 return 0;
 199         type = get_type(expr);
 200         if (!type)
 201                 return 0;
 202
 203         if (type->type == SYM_PTR)
 204                 type = get_base_type(type);
 205
 206         ret = bits_to_bytes(type->bit_size);
 207         if (ret == -1)
 208                 return 0;
 209         if (ret == 1)
 210                 return 0;  /* ignore char pointers */
 211
 212         return ret;
 213 }
 214
 215 static int get_size_from_strlen(struct expression *expr)
 216 {
 217         struct smatch_state *state;
 218         long long len;
 219
 220         state = get_state_expr(my_strlen_id, expr);
 221         if (!state || !state->data)
 222                 return 0;
 223         if (get_implied_max((struct expression *)state->data, &len))
 224                 return len + 1; /* add one because strlen doesn't include the NULL */
 225         return 0;
 226 }
 227
 228 static struct expression *remove_addr_fluff(struct expression *expr)
 229 {
 230         struct expression *tmp;
 231         long long val;
 232
 233         expr = strip_expr(expr);
 234
 235         /* remove '&' and '*' operations that cancel */
 236         while (expr->type == EXPR_PREOP && expr->op == '&') {
 237                 tmp = strip_expr(expr->unop);
 238                 if (tmp->type != EXPR_PREOP)
 239                         break;
 240                 if (tmp->op != '*')
 241                         break;
 242                 expr = strip_expr(tmp->unop);
 243         }
 244
 245         /* "foo + 0" is just "foo" */
 246         if (expr->type == EXPR_BINOP && expr->op == '+' &&
 247             get_value(expr->right, &val) && val == 0)
 248                 return expr->left;
 249
 250         return expr;
 251 }
 252
 253 int get_array_size_bytes(struct expression *expr)
 254 {
 255         int size;
 256
 257         expr = remove_addr_fluff(expr);
 258         if (!expr)
 259                 return 0;
 260
 261         /* strcpy(foo, "BAR"); */
 262         if (expr->type == EXPR_STRING)
 263                 return expr->string->length;
 264
 265         /* buf[4] */
 266         size = get_real_array_size(expr);
 267         if (size)
 268                 return elements_to_bytes(expr, size);
 269
 270         /* buf = malloc(1024); */
 271         size = get_stored_size_bytes(expr);
 272         if (size)
 273                 return size;
 274
 275         /* char *foo = "BAR" */
 276         size = get_size_from_initializer(expr);
 277         if (size)
 278                 return elements_to_bytes(expr, size);
 279
 280         size = get_bytes_from_address(expr);
 281         if (size)
 282                 return size;
 283
 284         /* if (strlen(foo) > 4) */
 285         size = get_size_from_strlen(expr);
 286         if (size)
 287                 return size;
 288
 289         return size_from_db(expr);
 290 }
 291
 292 int get_array_size(struct expression *expr)
 293 {
 294         int bytes;
 295
 296         bytes = get_array_size_bytes(expr);
 297         return bytes_to_elements(expr, bytes);
 298 }
 299
 300 static void match_strlen_condition(struct expression *expr)
 301 {
 302         struct expression *left;
 303         struct expression *right;
 304         struct expression *str = NULL;
 305         int strlen_left = 0;
 306         int strlen_right = 0;
 307         long long val;
 308         struct smatch_state *true_state = NULL;
 309         struct smatch_state *false_state = NULL;
 310
 311         if (expr->type != EXPR_COMPARE)
 312                 return;
 313         left = strip_expr(expr->left);
 314         right = strip_expr(expr->right);
 315
 316         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 317                 str = get_argument_from_call_expr(left->args, 0);
 318                 strlen_left = 1;
 319         }
 320         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 321                 str = get_argument_from_call_expr(right->args, 0);
 322                 strlen_right = 1;
 323         }
 324
 325         if (!strlen_left && !strlen_right)
 326                 return;
 327         if (strlen_left && strlen_right)
 328                 return;
 329
 330         if (strlen_left) {
 331                 if (!get_value(right, &val))
 332                         return;
 333         }
 334         if (strlen_right) {
 335                 if (!get_value(left, &val))
 336                         return;
 337         }
 338
 339         if (expr->op == SPECIAL_EQUAL) {
 340                 set_true_false_states_expr(my_size_id, str, alloc_state_num(val + 1), NULL);
 341                 return;
 342         }
 343         if (expr->op == SPECIAL_NOTEQUAL) {
 344                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(val + 1));
 345                 return;
 346         }
 347
 348         switch (expr->op) {
 349         case '<':
 350         case SPECIAL_UNSIGNED_LT:
 351                 if (strlen_left)
 352                         true_state = alloc_state_num(val);
 353                 else
 354                         false_state = alloc_state_num(val + 1);
 355                 break;
 356         case SPECIAL_LTE:
 357         case SPECIAL_UNSIGNED_LTE:
 358                 if (strlen_left)
 359                         true_state = alloc_state_num(val + 1);
 360                 else
 361                         false_state = alloc_state_num(val);
 362                 break;
 363         case SPECIAL_GTE:
 364         case SPECIAL_UNSIGNED_GTE:
 365                 if (strlen_left)
 366                         false_state = alloc_state_num(val);
 367                 else
 368                         true_state = alloc_state_num(val + 1);
 369                 break;
 370         case '>':
 371         case SPECIAL_UNSIGNED_GT:
 372                 if (strlen_left)
 373                         false_state = alloc_state_num(val + 1);
 374                 else
 375                         true_state = alloc_state_num(val);
 376                 break;
 377         }
 378         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 379 }
 380
 381 static struct expression *strip_ampersands(struct expression *expr)
 382 {
 383         struct symbol *type;
 384
 385         if (expr->type != EXPR_PREOP)
 386                 return expr;
 387         if (expr->op != '&')
 388                 return expr;
 389         type = get_type(expr->unop);
 390         if (!type || type->type != SYM_ARRAY)
 391                 return expr;
 392         return expr->unop;
 393 }
 394
 395 static void match_array_assignment(struct expression *expr)
 396 {
 397         struct expression *left;
 398         struct expression *right;
 399         int array_size;
 400
 401         if (expr->op != '=')
 402                 return;
 403         left = strip_expr(expr->left);
 404         right = strip_expr(expr->right);
 405         right = strip_ampersands(right);
 406         array_size = get_array_size_bytes(right);
 407         if (array_size)
 408                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 409 }
 410
 411 static void info_record_alloction(struct expression *buffer, struct expression *size)
 412 {
 413         char *member;
 414         long long val;
 415
 416         if (!option_info)
 417                 return;
 418         member = get_member_name(buffer);
 419         if (!member)
 420                 return;
 421         if (!get_implied_value(size, &val))
 422                 val = -1;
 423         sm_msg("info: '%s' allocated_buf_size %lld", member, val);
 424         free_string(member);
 425 }
 426
 427 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 428 {
 429         int size_arg = PTR_INT(_size_arg);
 430         struct expression *right;
 431         struct expression *arg;
 432         long long bytes;
 433
 434         right = strip_expr(expr->right);
 435         arg = get_argument_from_call_expr(right->args, size_arg);
 436
 437         info_record_alloction(expr->left, arg);
 438
 439         if (!get_implied_value(arg, &bytes))
 440                 return;
 441         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes));
 442 }
 443
 444 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 445 {
 446         struct expression *right;
 447         struct expression *arg;
 448         long long elements;
 449         long long size;
 450
 451         right = strip_expr(expr->right);
 452         arg = get_argument_from_call_expr(right->args, 0);
 453         if (!get_implied_value(arg, &elements))
 454                 return;
 455         arg = get_argument_from_call_expr(right->args, 1);
 456         if (!get_implied_value(arg, &size))
 457                 return;
 458         set_state_expr(my_size_id, expr->left, alloc_state_num(elements * size));
 459 }
 460
 461 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 462 {
 463         struct expression *right;
 464         struct expression *str;
 465         struct expression *len_expr;
 466         char *len_name;
 467         struct smatch_state *state;
 468
 469         right = strip_expr(expr->right);
 470         str = get_argument_from_call_expr(right->args, 0);
 471         len_expr = strip_expr(expr->left);
 472
 473         len_name = get_variable_from_expr(len_expr, NULL);
 474         if (!len_name)
 475                 return;
 476
 477         state = __alloc_smatch_state(0);
 478         state->name = len_name;
 479         state->data = len_expr;
 480         set_state_expr(my_strlen_id, str, state);
 481 }
 482
 483 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 484 {
 485         struct limiter *limiter = (struct limiter *)_limiter;
 486         struct expression *dest;
 487         struct expression *size_expr;
 488         long long size;
 489
 490         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 491         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 492         if (!get_implied_max(size_expr, &size))
 493                 return;
 494         set_state_expr(my_size_id, dest, alloc_state_num(size));
 495 }
 496
 497 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 498 {
 499         struct expression fake_assign;
 500
 501         fake_assign.op = '=';
 502         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 503         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 504         match_array_assignment(&fake_assign);
 505 }
 506
 507 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 508 {
 509         struct expression *fn_expr;
 510         struct expression *size_expr;
 511         long long size;
 512
 513         fn_expr = strip_expr(expr->right);
 514         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 515         if (!get_implied_max(size_expr, &size))
 516                 return;
 517
 518         /* It's easy to forget space for the NUL char */
 519         size++;
 520         set_state_expr(my_size_id, expr->left, alloc_state_num(size));
 521 }
 522
 523 static void match_call(struct expression *expr)
 524 {
 525         char *name;
 526         struct expression *arg;
 527         int bytes;
 528         int i;
 529
 530         name = get_fnptr_name(expr->fn);
 531         if (!name)
 532                 return;
 533
 534         i = 0;
 535         FOR_EACH_PTR(expr->args, arg) {
 536                 bytes = get_array_size_bytes(arg);
 537                 if (bytes > 1)
 538                         sm_msg("info: passes_buffer '%s' %d '$$' %d %s",
 539                                 name, i, bytes,
 540                                 is_static(expr->fn) ? "static" : "global");
 541                 i++;
 542         } END_FOR_EACH_PTR(arg);
 543
 544         free_string(name);
 545 }
 546
 547 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 548 {
 549         if (state == &merged)
 550                 return;
 551         sm_msg("info: passes_buffer '%s' %d '%s' %s %s", fn, param, printed_name, state->name, global_static);
 552 }
 553
 554 static void match_func_end(struct symbol *sym)
 555 {
 556         memset(params_set, 0, sizeof(params_set));
 557 }
 558
 559 void register_buf_size(int id)
 560 {
 561         my_size_id = id;
 562
 563         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 564
 565         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 566         add_function_assign_hook("calloc", &match_calloc, NULL);
 567         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 568         if (option_project == PROJ_KERNEL) {
 569                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 570                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 571                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 572                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 573                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 574                 add_function_assign_hook("kmalloc_array", &match_calloc, NULL);
 575                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 576                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 577                 add_function_assign_hook("sock_kmalloc", &match_alloc, INT_PTR(1));
 578                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 579                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 580         }
 581         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 582         add_hook(&match_strlen_condition, CONDITION_HOOK);
 583         add_function_assign_hook("strlen", &match_strlen, NULL);
 584
 585         add_function_assign_hook("strndup", match_strndup, NULL);
 586         if (option_project == PROJ_KERNEL)
 587                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 588
 589         add_hook(&match_func_end, END_FUNC_HOOK);
 590         add_modification_hook(my_size_id, &set_undefined);
 591 }
 592
 593 void register_strlen(int id)
 594 {
 595         my_strlen_id = id;
 596         add_modification_hook(my_strlen_id, &set_undefined);
 597 }
 598
 599 void register_buf_size_late(int id)
 600 {
 601         add_function_hook("strlcpy", &match_limited, &b0_l2);
 602         add_function_hook("strlcat", &match_limited, &b0_l2);
 603         add_function_hook("memscan", &match_limited, &b0_l2);
 604
 605         add_function_hook("strcpy", &match_strcpy, NULL);
 606
 607         if (option_info) {
 608                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 609                 add_member_info_callback(my_size_id, struct_member_callback);
 610         }
 611 }