check_user_data.c

   1 /*
   2  * Copyright (C) 2011 Dan Carpenter.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 /*
  19  * There are a couple checks that try to see if a variable
  20  * comes from the user.  It would be better to unify them
  21  * into one place.  Also it we should follow the data down
  22  * the call paths.  Hence this file.
  23  */
  24
  25 #include "smatch.h"
  26 #include "smatch_slist.h"
  27 #include "smatch_extra.h"
  28
  29 static int my_id;
  30
  31 STATE(capped);
  32 STATE(user_data_passed);
  33 STATE(user_data_set);
  34
  35 enum {
  36         SET_DATA = 1,
  37         PASSED_DATA = 2,
  38 };
  39
  40 int is_user_macro(struct expression *expr)
  41 {
  42         char *macro;
  43         struct range_list *rl;
  44
  45         macro = get_macro_name(expr->pos);
  46
  47         if (!macro)
  48                 return 0;
  49         if (get_implied_rl(expr, &rl) && !is_whole_rl(rl))
  50                 return 0;
  51         if (strcmp(macro, "ntohl") == 0)
  52                 return SET_DATA;
  53         if (strcmp(macro, "ntohs") == 0)
  54                 return SET_DATA;
  55         return 0;
  56 }
  57
  58 static int has_user_data_state(struct expression *expr)
  59 {
  60         struct stree *stree;
  61         struct sm_state *sm;
  62         struct symbol *sym;
  63         char *name;
  64
  65         expr = strip_expr(expr);
  66         if (expr->type == EXPR_PREOP && expr->op == '&')
  67                 expr = strip_expr(expr->unop);
  68
  69         name = expr_to_str_sym(expr, &sym);
  70         free_string(name);
  71         if (!sym)
  72                 return 1;
  73
  74         stree = __get_cur_stree();
  75         FOR_EACH_MY_SM(my_id, stree, sm) {
  76                 if (sm->sym == sym)
  77                         return 1;
  78         } END_FOR_EACH_SM(sm);
  79         return 0;
  80 }
  81
  82 static int passes_user_data(struct expression *expr)
  83 {
  84         struct expression *arg;
  85
  86         FOR_EACH_PTR(expr->args, arg) {
  87                 if (is_user_data(arg))
  88                         return 1;
  89                 if (has_user_data_state(arg))
  90                         return 1;
  91         } END_FOR_EACH_PTR(arg);
  92
  93         return 0;
  94 }
  95
  96 static struct expression *db_expr;
  97 static int db_user_data;
  98 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
  99 {
 100         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
 101                 return 0;
 102         db_user_data = 1;
 103         return 0;
 104 }
 105
 106 static int is_user_fn_db(struct expression *expr)
 107 {
 108         struct symbol *sym;
 109         static char sql_filter[1024];
 110
 111         if (is_fake_call(expr))
 112                 return 0;
 113         if (expr->fn->type != EXPR_SYMBOL)
 114                 return 0;
 115         sym = expr->fn->symbol;
 116         if (!sym)
 117                 return 0;
 118
 119         if (sym->ctype.modifiers & MOD_STATIC) {
 120                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 121                          get_filename(), sym->ident->name);
 122         } else {
 123                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 124                                 sym->ident->name);
 125         }
 126
 127         db_expr = expr;
 128         db_user_data = 0;
 129         run_sql(db_user_data_callback,
 130                 "select value from return_states where type=%d and parameter = -1 and key = '$$' and %s",
 131                 USER_DATA, sql_filter);
 132         return db_user_data;
 133 }
 134
 135 static int is_user_function(struct expression *expr)
 136 {
 137         if (expr->type != EXPR_CALL)
 138                 return 0;
 139         return is_user_fn_db(expr);
 140 }
 141
 142 static int is_skb_data(struct expression *expr)
 143 {
 144         struct symbol *sym;
 145         char *name;
 146         int len;
 147         int ret = 0;
 148
 149         name = expr_to_var_sym(expr, &sym);
 150         if (!name || !sym)
 151                 goto free;
 152
 153         sym = get_base_type(sym);
 154         if (!sym || sym->type != SYM_PTR)
 155                 goto free;
 156         sym = get_base_type(sym);
 157         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 158                 goto free;
 159         if (strcmp(sym->ident->name, "sk_buff") != 0)
 160                 goto free;
 161
 162         len = strlen(name);
 163         if (len < 6)
 164                 goto free;
 165         if (strcmp(name + len - 6, "->data") == 0)
 166                 ret = SET_DATA;
 167
 168 free:
 169         free_string(name);
 170         return ret;
 171 }
 172
 173 static int in_container_of_macro(struct expression *expr)
 174 {
 175         char *macro;
 176
 177         macro = get_macro_name(expr->pos);
 178
 179         if (!macro)
 180                 return 0;
 181         if (strcmp(macro, "container_of") == 0)
 182                 return 1;
 183         return 0;
 184 }
 185
 186 static int is_user_data_state(struct expression *expr)
 187 {
 188         struct stree *stree = NULL;
 189         struct sm_state *tmp;
 190         struct symbol *sym;
 191         char *name;
 192         int user = 0;
 193
 194         tmp = get_sm_state_expr(my_id, expr);
 195         if (tmp) {
 196                 if (slist_has_state(tmp->possible, &user_data_set))
 197                         return SET_DATA;
 198                 if (slist_has_state(tmp->possible, &user_data_passed))
 199                         return PASSED_DATA;
 200                 return 0;
 201         }
 202
 203         name = expr_to_str_sym(expr, &sym);
 204         if (!name || !sym)
 205                 goto free;
 206
 207         stree = __get_cur_stree();
 208         FOR_EACH_MY_SM(my_id, stree, tmp) {
 209                 if (tmp->sym != sym)
 210                         continue;
 211                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 212                         if (slist_has_state(tmp->possible, &user_data_set))
 213                                 user = SET_DATA;
 214                         else if (slist_has_state(tmp->possible, &user_data_passed))
 215                                 user = PASSED_DATA;
 216                         goto free;
 217                 }
 218         } END_FOR_EACH_SM(tmp);
 219
 220 free:
 221         free_string(name);
 222         return user;
 223 }
 224
 225 int is_user_data(struct expression *expr)
 226 {
 227         int user_data;
 228
 229         if (!expr)
 230                 return 0;
 231
 232         if (is_capped(expr))
 233                 return 0;
 234         if (in_container_of_macro(expr))
 235                 return 0;
 236
 237         user_data = is_user_macro(expr);
 238         if (user_data)
 239                 return user_data;
 240         user_data = is_user_function(expr);
 241         if (user_data)
 242                 return user_data;
 243         user_data = is_skb_data(expr);
 244         if (user_data)
 245                 return user_data;
 246
 247         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 248
 249         if (expr->type == EXPR_BINOP) {
 250                 user_data = is_user_data(expr->left);
 251                 if (user_data)
 252                         return user_data;
 253                 if (is_array(expr))
 254                         return 0;
 255                 user_data = is_user_data(expr->right);
 256                 if (user_data)
 257                         return user_data;
 258                 return 0;
 259         }
 260         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 261                 expr = strip_expr(expr->unop);
 262
 263         return is_user_data_state(expr);
 264 }
 265
 266 int implied_user_data(struct expression *expr, struct range_list **rl)
 267 {
 268         if (!is_user_data(expr))
 269                 return 0;
 270         get_absolute_rl(expr, rl);
 271         return 1;
 272 }
 273
 274 int is_capped_user_data(struct expression *expr)
 275 {
 276         struct sm_state *sm;
 277
 278         sm = get_sm_state_expr(my_id, expr);
 279         if (!sm)
 280                 return 0;
 281         if (slist_has_state(sm->possible, &capped))
 282                 return 1;
 283         return 0;
 284 }
 285
 286 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 287 {
 288         char fullname[256];
 289
 290         /* sanity check.  this should always be true. */
 291         if (strncmp(key, "$$", 2) != 0)
 292                 return;
 293         snprintf(fullname, 256, "%s%s", name, key + 2);
 294         set_state(my_id, fullname, sym, &user_data_passed);
 295 }
 296
 297 static void match_syscall_definition(struct symbol *sym)
 298 {
 299         struct symbol *arg;
 300         char *macro;
 301
 302         macro = get_macro_name(sym->pos);
 303         if (!macro)
 304                 return;
 305         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 306             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 307                 return;
 308
 309         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 310                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 311         } END_FOR_EACH_PTR(arg);
 312 }
 313
 314 static void match_condition(struct expression *expr)
 315 {
 316         switch (expr->op) {
 317         case '<':
 318         case SPECIAL_LTE:
 319         case SPECIAL_UNSIGNED_LT:
 320         case SPECIAL_UNSIGNED_LTE:
 321                 if (is_user_data(expr->left))
 322                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 323                 if (is_user_data(expr->right))
 324                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 325                 break;
 326         case '>':
 327         case SPECIAL_GTE:
 328         case SPECIAL_UNSIGNED_GT:
 329         case SPECIAL_UNSIGNED_GTE:
 330                 if (is_user_data(expr->right))
 331                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 332                 if (is_user_data(expr->left))
 333                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 334                 break;
 335         case SPECIAL_EQUAL:
 336                 if (is_user_data(expr->left))
 337                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 338                 if (is_user_data(expr->right))
 339                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 340                 break;
 341         case SPECIAL_NOTEQUAL:
 342                 if (is_user_data(expr->left))
 343                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 344                 if (is_user_data(expr->right))
 345                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 346                 break;
 347         default:
 348                 return;
 349         }
 350 }
 351
 352 static int handle_get_user(struct expression *expr)
 353 {
 354         char *name;
 355         int ret = 0;
 356
 357         name = get_macro_name(expr->pos);
 358         if (!name || strcmp(name, "get_user") != 0)
 359                 return 0;
 360
 361         name = expr_to_var(expr->right);
 362         if (!name || strcmp(name, "__val_gu") != 0)
 363                 goto free;
 364         set_state_expr(my_id, expr->left, &user_data_set);
 365         ret = 1;
 366 free:
 367         free_string(name);
 368         return ret;
 369 }
 370
 371 static void match_assign(struct expression *expr)
 372 {
 373         int user_data;
 374
 375         if (handle_get_user(expr))
 376                 return;
 377
 378         user_data = is_user_data(expr->right);
 379         if (user_data == PASSED_DATA)
 380                 set_state_expr(my_id, expr->left, &user_data_passed);
 381         else if (user_data == SET_DATA)
 382                 set_state_expr(my_id, expr->left, &user_data_set);
 383         else if (get_state_expr(my_id, expr->left))
 384                 set_state_expr(my_id, expr->left, &capped);
 385 }
 386
 387 static void tag_struct_members(struct symbol *type, struct expression *expr)
 388 {
 389         struct symbol *tmp;
 390         struct expression *member;
 391         int op = '*';
 392
 393         if (expr->type == EXPR_PREOP && expr->op == '&') {
 394                 expr = strip_expr(expr->unop);
 395                 op = '.';
 396         }
 397
 398         FOR_EACH_PTR(type->symbol_list, tmp) {
 399                 if (!tmp->ident)
 400                         continue;
 401                 member = member_expression(expr, op, tmp->ident);
 402                 set_state_expr(my_id, member, &user_data_set);
 403         } END_FOR_EACH_PTR(tmp);
 404 }
 405
 406 static void tag_base_type(struct expression *expr)
 407 {
 408         if (expr->type == EXPR_PREOP && expr->op == '&')
 409                 expr = strip_expr(expr->unop);
 410         else
 411                 expr = deref_expression(expr);
 412         set_state_expr(my_id, expr, &user_data_set);
 413 }
 414
 415 static void tag_as_user_data(struct expression *expr)
 416 {
 417         struct symbol *type;
 418
 419         expr = strip_expr(expr);
 420
 421         type = get_type(expr);
 422         if (!type || type->type != SYM_PTR)
 423                 return;
 424         type = get_real_base_type(type);
 425         if (!type)
 426                 return;
 427         if (type == &void_ctype) {
 428                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 429                 return;
 430         }
 431         if (type->type == SYM_BASETYPE)
 432                 tag_base_type(expr);
 433         if (type->type == SYM_STRUCT) {
 434                 if (expr->type != EXPR_PREOP || expr->op != '&')
 435                         expr = deref_expression(expr);
 436                 tag_struct_members(type, expr);
 437         }
 438 }
 439
 440 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 441 {
 442         int param = PTR_INT(_param);
 443         struct expression *dest;
 444
 445         dest = get_argument_from_call_expr(expr->args, param);
 446         dest = strip_expr(dest);
 447         if (!dest)
 448                 return;
 449         tag_as_user_data(dest);
 450 }
 451
 452 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 453 {
 454         set_state_expr(my_id, expr->left, &user_data_set);
 455 }
 456
 457 static void match_caller_info(struct expression *expr)
 458 {
 459         struct expression *tmp;
 460         int i;
 461
 462         i = 0;
 463         FOR_EACH_PTR(expr->args, tmp) {
 464                 if (is_user_data(tmp))
 465                         sql_insert_caller_info(expr, USER_DATA, i, "$$", "");
 466                 i++;
 467         } END_FOR_EACH_PTR(tmp);
 468 }
 469
 470 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 471 {
 472         if (state == &capped)
 473                 return;
 474         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 475 }
 476
 477 static void returned_member_callback(int return_id, char *return_ranges, char *printed_name, struct smatch_state *state)
 478 {
 479         if (state == &capped)
 480                 return;
 481         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 482 }
 483
 484 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 485 {
 486         struct stree *stree;
 487         struct sm_state *tmp;
 488         int param;
 489         int user_data;
 490         const char *passed_or_new;
 491
 492         user_data = is_user_data(expr);
 493         if (user_data == PASSED_DATA) {
 494                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 495                                 -1, "$$", "2");
 496         }
 497         if (user_data == SET_DATA) {
 498                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 499                                 -1, "$$", "1");
 500         }
 501
 502         stree = __get_cur_stree();
 503
 504         FOR_EACH_MY_SM(my_id, stree, tmp) {
 505                 const char *param_name;
 506
 507                 param = get_param_num_from_sym(tmp->sym);
 508                 if (param < 0)
 509                         continue;
 510
 511                 if (is_capped_var_sym(tmp->name, tmp->sym))
 512                         continue;
 513                 /* ignore states that were already USER_DATA to begin with */
 514                 if (get_state_stree(get_start_states(), my_id, tmp->name, tmp->sym))
 515                         continue;
 516
 517                 param_name = get_param_name(tmp);
 518                 if (!param_name || strcmp(param_name, "$$") == 0)
 519                         continue;
 520
 521                 if (slist_has_state(tmp->possible, &user_data_set))
 522                         passed_or_new = "1";
 523                 else if (slist_has_state(tmp->possible, &user_data_passed))
 524                         passed_or_new = "2";
 525                 else
 526                         continue;
 527
 528                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 529                                 param, param_name, passed_or_new);
 530         } END_FOR_EACH_SM(tmp);
 531 }
 532
 533 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 534 {
 535         char *name;
 536         struct symbol *sym;
 537
 538         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$$") == 0) {
 539                 tag_as_user_data(expr->left);
 540                 return;
 541         }
 542
 543         name = return_state_to_var_sym(expr, param, key, &sym);
 544         if (!name || !sym)
 545                 goto free;
 546
 547         set_state(my_id, name, sym, &user_data_set);
 548 free:
 549         free_string(name);
 550 }
 551
 552 void check_user_data(int id)
 553 {
 554         if (option_project != PROJ_KERNEL)
 555                 return;
 556         my_id = id;
 557         select_caller_info_hook(set_param_user_data, USER_DATA);
 558         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 559         add_hook(&match_condition, CONDITION_HOOK);
 560         add_hook(&match_assign, ASSIGNMENT_HOOK);
 561         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 562         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 563         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 564         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 565
 566         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 567         add_member_info_callback(my_id, struct_member_callback);
 568         add_returned_member_callback(my_id, returned_member_callback);
 569         add_split_return_callback(print_returned_user_data);
 570         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 571 }