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