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(called);
  32
  33 STATE(capped);
  34 STATE(user_data_passed);
  35 STATE(user_data_set);
  36
  37 enum {
  38         SET_DATA = 1,
  39         PASSED_DATA = 2,
  40 };
  41
  42 int is_user_macro(struct expression *expr)
  43 {
  44         char *macro;
  45         struct range_list *rl;
  46
  47         macro = get_macro_name(expr->pos);
  48
  49         if (!macro)
  50                 return 0;
  51         if (get_implied_rl(expr, &rl) && !is_whole_rl(rl))
  52                 return 0;
  53         if (strcmp(macro, "ntohl") == 0)
  54                 return SET_DATA;
  55         if (strcmp(macro, "ntohs") == 0)
  56                 return SET_DATA;
  57         return 0;
  58 }
  59
  60 static int has_user_data_state(struct expression *expr)
  61 {
  62         struct stree *stree;
  63         struct sm_state *sm;
  64         struct symbol *sym;
  65         char *name;
  66
  67         expr = strip_expr(expr);
  68         if (expr->type == EXPR_PREOP && expr->op == '&')
  69                 expr = strip_expr(expr->unop);
  70
  71         name = expr_to_str_sym(expr, &sym);
  72         free_string(name);
  73         if (!sym)
  74                 return 1;
  75
  76         stree = __get_cur_stree();
  77         FOR_EACH_MY_SM(my_id, stree, sm) {
  78                 if (sm->sym == sym)
  79                         return 1;
  80         } END_FOR_EACH_SM(sm);
  81         return 0;
  82 }
  83
  84 static int passes_user_data(struct expression *expr)
  85 {
  86         struct expression *arg;
  87
  88         FOR_EACH_PTR(expr->args, arg) {
  89                 if (is_user_data(arg))
  90                         return 1;
  91                 if (has_user_data_state(arg))
  92                         return 1;
  93         } END_FOR_EACH_PTR(arg);
  94
  95         return 0;
  96 }
  97
  98 static struct expression *db_expr;
  99 static int db_user_data;
 100 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
 101 {
 102         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
 103                 return 0;
 104         db_user_data = 1;
 105         return 0;
 106 }
 107
 108 static int is_user_fn_db(struct expression *expr)
 109 {
 110         struct symbol *sym;
 111         static char sql_filter[1024];
 112
 113         if (is_fake_call(expr))
 114                 return 0;
 115         if (expr->fn->type != EXPR_SYMBOL)
 116                 return 0;
 117         sym = expr->fn->symbol;
 118         if (!sym)
 119                 return 0;
 120
 121         if (sym->ctype.modifiers & MOD_STATIC) {
 122                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 123                          get_filename(), sym->ident->name);
 124         } else {
 125                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 126                                 sym->ident->name);
 127         }
 128
 129         db_expr = expr;
 130         db_user_data = 0;
 131         run_sql(db_user_data_callback, NULL,
 132                 "select value from return_states where type=%d and parameter = -1 and key = '$' and %s",
 133                 USER_DATA, sql_filter);
 134         return db_user_data;
 135 }
 136
 137 static int is_user_function(struct expression *expr)
 138 {
 139         if (expr->type != EXPR_CALL)
 140                 return 0;
 141         return is_user_fn_db(expr);
 142 }
 143
 144 static int is_skb_data(struct expression *expr)
 145 {
 146         struct symbol *sym;
 147         char *name;
 148         int len;
 149         int ret = 0;
 150
 151         name = expr_to_var_sym(expr, &sym);
 152         if (!name || !sym)
 153                 goto free;
 154
 155         sym = get_base_type(sym);
 156         if (!sym || sym->type != SYM_PTR)
 157                 goto free;
 158         sym = get_base_type(sym);
 159         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 160                 goto free;
 161         if (strcmp(sym->ident->name, "sk_buff") != 0)
 162                 goto free;
 163
 164         len = strlen(name);
 165         if (len < 6)
 166                 goto free;
 167         if (strcmp(name + len - 6, "->data") == 0)
 168                 ret = SET_DATA;
 169
 170 free:
 171         free_string(name);
 172         return ret;
 173 }
 174
 175 static int in_container_of_macro(struct expression *expr)
 176 {
 177         char *macro;
 178
 179         macro = get_macro_name(expr->pos);
 180
 181         if (!macro)
 182                 return 0;
 183         if (strcmp(macro, "container_of") == 0)
 184                 return 1;
 185         return 0;
 186 }
 187
 188 static int is_user_data_state(struct expression *expr)
 189 {
 190         struct stree *stree = NULL;
 191         struct sm_state *tmp;
 192         struct symbol *sym;
 193         char *name;
 194         int user = 0;
 195
 196         tmp = get_sm_state_expr(my_id, expr);
 197         if (tmp) {
 198                 if (slist_has_state(tmp->possible, &user_data_set))
 199                         return SET_DATA;
 200                 if (slist_has_state(tmp->possible, &user_data_passed))
 201                         return PASSED_DATA;
 202                 return 0;
 203         }
 204
 205         name = expr_to_str_sym(expr, &sym);
 206         if (!name || !sym)
 207                 goto free;
 208
 209         stree = __get_cur_stree();
 210         FOR_EACH_MY_SM(my_id, stree, tmp) {
 211                 if (tmp->sym != sym)
 212                         continue;
 213                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 214                         if (slist_has_state(tmp->possible, &user_data_set))
 215                                 user = SET_DATA;
 216                         else if (slist_has_state(tmp->possible, &user_data_passed))
 217                                 user = PASSED_DATA;
 218                         goto free;
 219                 }
 220         } END_FOR_EACH_SM(tmp);
 221
 222 free:
 223         free_string(name);
 224         return user;
 225 }
 226
 227 int is_user_data(struct expression *expr)
 228 {
 229         int user_data;
 230
 231         if (!expr)
 232                 return 0;
 233
 234         if (is_capped(expr))
 235                 return 0;
 236         if (in_container_of_macro(expr))
 237                 return 0;
 238
 239         user_data = is_user_macro(expr);
 240         if (user_data)
 241                 return user_data;
 242         user_data = is_user_function(expr);
 243         if (user_data)
 244                 return user_data;
 245         user_data = is_skb_data(expr);
 246         if (user_data)
 247                 return user_data;
 248
 249         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 250
 251         if (expr->type == EXPR_BINOP) {
 252                 user_data = is_user_data(expr->left);
 253                 if (user_data)
 254                         return user_data;
 255                 if (is_array(expr))
 256                         return 0;
 257                 user_data = is_user_data(expr->right);
 258                 if (user_data)
 259                         return user_data;
 260                 return 0;
 261         }
 262         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 263                 expr = strip_expr(expr->unop);
 264
 265         return is_user_data_state(expr);
 266 }
 267
 268 int implied_user_data(struct expression *expr, struct range_list **rl)
 269 {
 270         if (!is_user_data(expr))
 271                 return 0;
 272         get_absolute_rl(expr, rl);
 273         return 1;
 274 }
 275
 276 int is_capped_user_data(struct expression *expr)
 277 {
 278         struct sm_state *sm;
 279
 280         sm = get_sm_state_expr(my_id, expr);
 281         if (!sm)
 282                 return 0;
 283         if (slist_has_state(sm->possible, &capped))
 284                 return 1;
 285         return 0;
 286 }
 287
 288 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 289 {
 290         set_state(my_id, "this_function", NULL, &called);
 291 }
 292
 293 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 294 {
 295         char fullname[256];
 296
 297         /* sanity check.  this should always be true. */
 298         if (strncmp(key, "$", 1) != 0)
 299                 return;
 300         snprintf(fullname, 256, "%s%s", name, key + 1);
 301         set_state(my_id, fullname, sym, &user_data_passed);
 302 }
 303
 304 static void match_syscall_definition(struct symbol *sym)
 305 {
 306         struct symbol *arg;
 307         char *macro;
 308         char *name;
 309         int is_syscall = 0;
 310
 311         macro = get_macro_name(sym->pos);
 312         if (macro &&
 313             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 314              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 315                 is_syscall = 1;
 316
 317         name = get_function();
 318         if (!option_no_db && get_state(my_id, "this_function", NULL) != &called) {
 319                 if (name && strncmp(name, "sys_", 4) == 0)
 320                         is_syscall = 1;
 321         }
 322
 323         if (name && strncmp(name, "compat_sys_", 11) == 0)
 324                 is_syscall = 1;
 325
 326         if (!is_syscall)
 327                 return;
 328
 329         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 330                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 331         } END_FOR_EACH_PTR(arg);
 332 }
 333
 334 static void match_condition(struct expression *expr)
 335 {
 336         switch (expr->op) {
 337         case '<':
 338         case SPECIAL_LTE:
 339         case SPECIAL_UNSIGNED_LT:
 340         case SPECIAL_UNSIGNED_LTE:
 341                 if (is_user_data(expr->left))
 342                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 343                 if (is_user_data(expr->right))
 344                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 345                 break;
 346         case '>':
 347         case SPECIAL_GTE:
 348         case SPECIAL_UNSIGNED_GT:
 349         case SPECIAL_UNSIGNED_GTE:
 350                 if (is_user_data(expr->right))
 351                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 352                 if (is_user_data(expr->left))
 353                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 354                 break;
 355         case SPECIAL_EQUAL:
 356                 if (is_user_data(expr->left))
 357                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 358                 if (is_user_data(expr->right))
 359                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 360                 break;
 361         case SPECIAL_NOTEQUAL:
 362                 if (is_user_data(expr->left))
 363                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 364                 if (is_user_data(expr->right))
 365                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 366                 break;
 367         default:
 368                 return;
 369         }
 370 }
 371
 372 static int handle_get_user(struct expression *expr)
 373 {
 374         char *name;
 375         int ret = 0;
 376
 377         name = get_macro_name(expr->pos);
 378         if (!name || strcmp(name, "get_user") != 0)
 379                 return 0;
 380
 381         name = expr_to_var(expr->right);
 382         if (!name || strcmp(name, "__val_gu") != 0)
 383                 goto free;
 384         set_state_expr(my_id, expr->left, &user_data_set);
 385         ret = 1;
 386 free:
 387         free_string(name);
 388         return ret;
 389 }
 390
 391 static void match_assign(struct expression *expr)
 392 {
 393         int user_data;
 394
 395         if (handle_get_user(expr))
 396                 return;
 397
 398         user_data = is_user_data(expr->right);
 399         if (user_data == PASSED_DATA)
 400                 set_state_expr(my_id, expr->left, &user_data_passed);
 401         else if (user_data == SET_DATA)
 402                 set_state_expr(my_id, expr->left, &user_data_set);
 403         else if (get_state_expr(my_id, expr->left))
 404                 set_state_expr(my_id, expr->left, &capped);
 405 }
 406
 407 static void tag_struct_members(struct symbol *type, struct expression *expr)
 408 {
 409         struct symbol *tmp;
 410         struct expression *member;
 411         int op = '*';
 412
 413         if (expr->type == EXPR_PREOP && expr->op == '&') {
 414                 expr = strip_expr(expr->unop);
 415                 op = '.';
 416         }
 417
 418         FOR_EACH_PTR(type->symbol_list, tmp) {
 419                 if (!tmp->ident)
 420                         continue;
 421                 member = member_expression(expr, op, tmp->ident);
 422                 set_state_expr(my_id, member, &user_data_set);
 423         } END_FOR_EACH_PTR(tmp);
 424 }
 425
 426 static void tag_base_type(struct expression *expr)
 427 {
 428         if (expr->type == EXPR_PREOP && expr->op == '&')
 429                 expr = strip_expr(expr->unop);
 430         else
 431                 expr = deref_expression(expr);
 432         set_state_expr(my_id, expr, &user_data_set);
 433 }
 434
 435 static void tag_as_user_data(struct expression *expr)
 436 {
 437         struct symbol *type;
 438
 439         expr = strip_expr(expr);
 440
 441         type = get_type(expr);
 442         if (!type || type->type != SYM_PTR)
 443                 return;
 444         type = get_real_base_type(type);
 445         if (!type)
 446                 return;
 447         if (type == &void_ctype) {
 448                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 449                 return;
 450         }
 451         if (type->type == SYM_BASETYPE)
 452                 tag_base_type(expr);
 453         if (type->type == SYM_STRUCT) {
 454                 if (expr->type != EXPR_PREOP || expr->op != '&')
 455                         expr = deref_expression(expr);
 456                 tag_struct_members(type, expr);
 457         }
 458 }
 459
 460 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 461 {
 462         int param = PTR_INT(_param);
 463         struct expression *dest;
 464
 465         dest = get_argument_from_call_expr(expr->args, param);
 466         dest = strip_expr(dest);
 467         if (!dest)
 468                 return;
 469         tag_as_user_data(dest);
 470 }
 471
 472 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 473 {
 474         set_state_expr(my_id, expr->left, &user_data_set);
 475 }
 476
 477 static void match_caller_info(struct expression *expr)
 478 {
 479         struct expression *tmp;
 480         int i;
 481
 482         i = 0;
 483         FOR_EACH_PTR(expr->args, tmp) {
 484                 if (is_user_data(tmp))
 485                         sql_insert_caller_info(expr, USER_DATA, i, "$", "");
 486                 i++;
 487         } END_FOR_EACH_PTR(tmp);
 488 }
 489
 490 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 491 {
 492         if (sm->state == &capped)
 493                 return;
 494         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 495 }
 496
 497 static void returned_member_callback(int return_id, char *return_ranges, struct expression *expr, char *printed_name, struct smatch_state *state)
 498 {
 499         if (state == &capped)
 500                 return;
 501         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 502 }
 503
 504 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 505 {
 506         struct stree *stree;
 507         struct sm_state *tmp;
 508         int param;
 509         int user_data;
 510         const char *passed_or_new;
 511
 512         user_data = is_user_data(expr);
 513         if (user_data == PASSED_DATA) {
 514                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 515                                 -1, "$", "2");
 516         }
 517         if (user_data == SET_DATA) {
 518                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 519                                 -1, "$", "1");
 520         }
 521
 522         stree = __get_cur_stree();
 523
 524         FOR_EACH_MY_SM(my_id, stree, tmp) {
 525                 const char *param_name;
 526
 527                 param = get_param_num_from_sym(tmp->sym);
 528                 if (param < 0)
 529                         continue;
 530
 531                 if (is_capped_var_sym(tmp->name, tmp->sym))
 532                         continue;
 533                 /* ignore states that were already USER_DATA to begin with */
 534                 if (get_state_stree(get_start_states(), my_id, tmp->name, tmp->sym))
 535                         continue;
 536
 537                 param_name = get_param_name(tmp);
 538                 if (!param_name || strcmp(param_name, "$") == 0)
 539                         continue;
 540
 541                 if (slist_has_state(tmp->possible, &user_data_set))
 542                         passed_or_new = "1";
 543                 else if (slist_has_state(tmp->possible, &user_data_passed))
 544                         passed_or_new = "2";
 545                 else
 546                         continue;
 547
 548                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 549                                 param, param_name, passed_or_new);
 550         } END_FOR_EACH_SM(tmp);
 551 }
 552
 553 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 554 {
 555         char *name;
 556         struct symbol *sym;
 557
 558         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$") == 0) {
 559                 tag_as_user_data(expr->left);
 560                 return;
 561         }
 562
 563         name = return_state_to_var_sym(expr, param, key, &sym);
 564         if (!name || !sym)
 565                 goto free;
 566
 567         set_state(my_id, name, sym, &user_data_set);
 568 free:
 569         free_string(name);
 570 }
 571
 572 void check_user_data(int id)
 573 {
 574         if (option_project != PROJ_KERNEL)
 575                 return;
 576         my_id = id;
 577         select_caller_info_hook(set_called, INTERNAL);
 578         select_caller_info_hook(set_param_user_data, USER_DATA);
 579         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 580         add_hook(&match_condition, CONDITION_HOOK);
 581         add_hook(&match_assign, ASSIGNMENT_HOOK);
 582         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 583         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 584         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 585         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 586         add_function_hook("_kstrtoull", &match_user_copy, INT_PTR(2));
 587
 588         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 589         add_member_info_callback(my_id, struct_member_callback);
 590         add_returned_member_callback(my_id, returned_member_callback);
 591         add_split_return_callback(print_returned_user_data);
 592         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 593 }