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 static const char * kstr_funcs[] = {
  38         "kstrtoull", "kstrtoll", "kstrtoul", "kstrtol", "kstrtouint",
  39         "kstrtoint", "kstrtou64", "kstrtos64", "kstrtou32", "kstrtos32",
  40         "kstrtou16", "kstrtos16", "kstrtou8", "kstrtos8", "kstrtoull_from_user"
  41         "kstrtoll_from_user", "kstrtoul_from_user", "kstrtol_from_user",
  42         "kstrtouint_from_user", "kstrtoint_from_user", "kstrtou16_from_user",
  43         "kstrtos16_from_user", "kstrtou8_from_user", "kstrtos8_from_user",
  44         "kstrtou64_from_user", "kstrtos64_from_user", "kstrtou32_from_user",
  45         "kstrtos32_from_user",
  46 };
  47
  48 enum {
  49         SET_DATA = 1,
  50         PASSED_DATA = 2,
  51 };
  52
  53 int is_user_macro(struct expression *expr)
  54 {
  55         char *macro;
  56         struct range_list *rl;
  57
  58         macro = get_macro_name(expr->pos);
  59
  60         if (!macro)
  61                 return 0;
  62         if (get_implied_rl(expr, &rl) && !is_whole_rl(rl))
  63                 return 0;
  64         if (strcmp(macro, "ntohl") == 0)
  65                 return SET_DATA;
  66         if (strcmp(macro, "ntohs") == 0)
  67                 return SET_DATA;
  68         return 0;
  69 }
  70
  71 static int has_user_data_state(struct expression *expr)
  72 {
  73         struct stree *stree;
  74         struct sm_state *sm;
  75         struct symbol *sym;
  76         char *name;
  77
  78         expr = strip_expr(expr);
  79         if (expr->type == EXPR_PREOP && expr->op == '&')
  80                 expr = strip_expr(expr->unop);
  81
  82         name = expr_to_str_sym(expr, &sym);
  83         free_string(name);
  84         if (!sym)
  85                 return 1;
  86
  87         stree = __get_cur_stree();
  88         FOR_EACH_MY_SM(my_id, stree, sm) {
  89                 if (sm->sym == sym)
  90                         return 1;
  91         } END_FOR_EACH_SM(sm);
  92         return 0;
  93 }
  94
  95 static int passes_user_data(struct expression *expr)
  96 {
  97         struct expression *arg;
  98
  99         FOR_EACH_PTR(expr->args, arg) {
 100                 if (is_user_data(arg))
 101                         return 1;
 102                 if (has_user_data_state(arg))
 103                         return 1;
 104         } END_FOR_EACH_PTR(arg);
 105
 106         return 0;
 107 }
 108
 109 static struct expression *db_expr;
 110 static int db_user_data;
 111 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
 112 {
 113         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
 114                 return 0;
 115         db_user_data = 1;
 116         return 0;
 117 }
 118
 119 static int is_user_fn_db(struct expression *expr)
 120 {
 121         struct symbol *sym;
 122         static char sql_filter[1024];
 123
 124         if (is_fake_call(expr))
 125                 return 0;
 126         if (expr->fn->type != EXPR_SYMBOL)
 127                 return 0;
 128         sym = expr->fn->symbol;
 129         if (!sym)
 130                 return 0;
 131
 132         if (sym->ctype.modifiers & MOD_STATIC) {
 133                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 134                          get_filename(), sym->ident->name);
 135         } else {
 136                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 137                                 sym->ident->name);
 138         }
 139
 140         db_expr = expr;
 141         db_user_data = 0;
 142         run_sql(db_user_data_callback, NULL,
 143                 "select value from return_states where type=%d and parameter = -1 and key = '$' and %s",
 144                 USER_DATA, sql_filter);
 145         return db_user_data;
 146 }
 147
 148 static int is_user_function(struct expression *expr)
 149 {
 150         if (expr->type != EXPR_CALL)
 151                 return 0;
 152         return is_user_fn_db(expr);
 153 }
 154
 155 static int is_skb_data(struct expression *expr)
 156 {
 157         struct symbol *sym;
 158         char *name;
 159         int len;
 160         int ret = 0;
 161
 162         name = expr_to_var_sym(expr, &sym);
 163         if (!name || !sym)
 164                 goto free;
 165
 166         sym = get_base_type(sym);
 167         if (!sym || sym->type != SYM_PTR)
 168                 goto free;
 169         sym = get_base_type(sym);
 170         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 171                 goto free;
 172         if (strcmp(sym->ident->name, "sk_buff") != 0)
 173                 goto free;
 174
 175         len = strlen(name);
 176         if (len < 6)
 177                 goto free;
 178         if (strcmp(name + len - 6, "->data") == 0)
 179                 ret = SET_DATA;
 180
 181 free:
 182         free_string(name);
 183         return ret;
 184 }
 185
 186 static int in_container_of_macro(struct expression *expr)
 187 {
 188         char *macro;
 189
 190         macro = get_macro_name(expr->pos);
 191
 192         if (!macro)
 193                 return 0;
 194         if (strcmp(macro, "container_of") == 0)
 195                 return 1;
 196         return 0;
 197 }
 198
 199 static int is_user_data_state(struct expression *expr)
 200 {
 201         struct stree *stree = NULL;
 202         struct sm_state *tmp;
 203         struct symbol *sym;
 204         char *name;
 205         int user = 0;
 206
 207         tmp = get_sm_state_expr(my_id, expr);
 208         if (tmp) {
 209                 if (slist_has_state(tmp->possible, &user_data_set))
 210                         return SET_DATA;
 211                 if (slist_has_state(tmp->possible, &user_data_passed))
 212                         return PASSED_DATA;
 213                 return 0;
 214         }
 215
 216         name = expr_to_str_sym(expr, &sym);
 217         if (!name || !sym)
 218                 goto free;
 219
 220         stree = __get_cur_stree();
 221         FOR_EACH_MY_SM(my_id, stree, tmp) {
 222                 if (tmp->sym != sym)
 223                         continue;
 224                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 225                         if (slist_has_state(tmp->possible, &user_data_set))
 226                                 user = SET_DATA;
 227                         else if (slist_has_state(tmp->possible, &user_data_passed))
 228                                 user = PASSED_DATA;
 229                         goto free;
 230                 }
 231         } END_FOR_EACH_SM(tmp);
 232
 233 free:
 234         free_string(name);
 235         return user;
 236 }
 237
 238 int is_user_data(struct expression *expr)
 239 {
 240         struct range_list *rl;
 241         int user_data;
 242
 243         if (is_capped(expr))
 244                 return 0;
 245         return get_user_rl(expr, &rl);
 246
 247         if (!expr)
 248                 return 0;
 249
 250         if (is_capped(expr))
 251                 return 0;
 252         if (in_container_of_macro(expr))
 253                 return 0;
 254
 255         user_data = is_user_macro(expr);
 256         if (user_data)
 257                 return user_data;
 258         user_data = is_user_function(expr);
 259         if (user_data)
 260                 return user_data;
 261         user_data = is_skb_data(expr);
 262         if (user_data)
 263                 return user_data;
 264
 265         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 266
 267         if (expr->type == EXPR_BINOP) {
 268                 user_data = is_user_data(expr->left);
 269                 if (user_data)
 270                         return user_data;
 271                 if (is_array(expr))
 272                         return 0;
 273                 user_data = is_user_data(expr->right);
 274                 if (user_data)
 275                         return user_data;
 276                 return 0;
 277         }
 278         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 279                 expr = strip_expr(expr->unop);
 280
 281         return is_user_data_state(expr);
 282 }
 283
 284 int implied_user_data(struct expression *expr, struct range_list **rl)
 285 {
 286         if (!is_user_data(expr))
 287                 return 0;
 288         get_absolute_rl(expr, rl);
 289         return 1;
 290 }
 291
 292 int is_capped_user_data(struct expression *expr)
 293 {
 294         struct sm_state *sm;
 295
 296         sm = get_sm_state_expr(my_id, expr);
 297         if (!sm)
 298                 return 0;
 299         if (slist_has_state(sm->possible, &capped))
 300                 return 1;
 301         return 0;
 302 }
 303
 304 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 305 {
 306         set_state(my_id, "this_function", NULL, &called);
 307 }
 308
 309 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 310 {
 311         char fullname[256];
 312
 313         /* sanity check.  this should always be true. */
 314         if (strncmp(key, "$", 1) != 0)
 315                 return;
 316         snprintf(fullname, 256, "%s%s", name, key + 1);
 317         set_state(my_id, fullname, sym, &user_data_passed);
 318 }
 319
 320 static void match_syscall_definition(struct symbol *sym)
 321 {
 322         struct symbol *arg;
 323         char *macro;
 324         char *name;
 325         int is_syscall = 0;
 326
 327         macro = get_macro_name(sym->pos);
 328         if (macro &&
 329             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 330              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 331                 is_syscall = 1;
 332
 333         name = get_function();
 334         if (!option_no_db && get_state(my_id, "this_function", NULL) != &called) {
 335                 if (name && strncmp(name, "sys_", 4) == 0)
 336                         is_syscall = 1;
 337         }
 338
 339         if (name && strncmp(name, "compat_sys_", 11) == 0)
 340                 is_syscall = 1;
 341
 342         if (!is_syscall)
 343                 return;
 344
 345         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 346                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 347         } END_FOR_EACH_PTR(arg);
 348 }
 349
 350 static void match_condition(struct expression *expr)
 351 {
 352         switch (expr->op) {
 353         case '<':
 354         case SPECIAL_LTE:
 355         case SPECIAL_UNSIGNED_LT:
 356         case SPECIAL_UNSIGNED_LTE:
 357                 if (is_user_data(expr->left))
 358                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 359                 if (is_user_data(expr->right))
 360                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 361                 break;
 362         case '>':
 363         case SPECIAL_GTE:
 364         case SPECIAL_UNSIGNED_GT:
 365         case SPECIAL_UNSIGNED_GTE:
 366                 if (is_user_data(expr->right))
 367                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 368                 if (is_user_data(expr->left))
 369                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 370                 break;
 371         case SPECIAL_EQUAL:
 372                 if (is_user_data(expr->left))
 373                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 374                 if (is_user_data(expr->right))
 375                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 376                 break;
 377         case SPECIAL_NOTEQUAL:
 378                 if (is_user_data(expr->left))
 379                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 380                 if (is_user_data(expr->right))
 381                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 382                 break;
 383         default:
 384                 return;
 385         }
 386 }
 387
 388 static int handle_get_user(struct expression *expr)
 389 {
 390         char *name;
 391         int ret = 0;
 392
 393         name = get_macro_name(expr->pos);
 394         if (!name || strcmp(name, "get_user") != 0)
 395                 return 0;
 396
 397         name = expr_to_var(expr->right);
 398         if (!name || strcmp(name, "__val_gu") != 0)
 399                 goto free;
 400         set_state_expr(my_id, expr->left, &user_data_set);
 401         ret = 1;
 402 free:
 403         free_string(name);
 404         return ret;
 405 }
 406
 407 static void match_assign(struct expression *expr)
 408 {
 409         int user_data;
 410
 411         if (handle_get_user(expr))
 412                 return;
 413
 414         user_data = is_user_data(expr->right);
 415         if (user_data == PASSED_DATA)
 416                 set_state_expr(my_id, expr->left, &user_data_passed);
 417         else if (user_data == SET_DATA)
 418                 set_state_expr(my_id, expr->left, &user_data_set);
 419         else if (get_state_expr(my_id, expr->left))
 420                 set_state_expr(my_id, expr->left, &capped);
 421 }
 422
 423 static void tag_struct_members(struct symbol *type, struct expression *expr)
 424 {
 425         struct symbol *tmp;
 426         struct expression *member;
 427         int op = '*';
 428
 429         if (expr->type == EXPR_PREOP && expr->op == '&') {
 430                 expr = strip_expr(expr->unop);
 431                 op = '.';
 432         }
 433
 434         FOR_EACH_PTR(type->symbol_list, tmp) {
 435                 if (!tmp->ident)
 436                         continue;
 437                 member = member_expression(expr, op, tmp->ident);
 438                 set_state_expr(my_id, member, &user_data_set);
 439         } END_FOR_EACH_PTR(tmp);
 440 }
 441
 442 static void tag_base_type(struct expression *expr)
 443 {
 444         if (expr->type == EXPR_PREOP && expr->op == '&')
 445                 expr = strip_expr(expr->unop);
 446         else
 447                 expr = deref_expression(expr);
 448         set_state_expr(my_id, expr, &user_data_set);
 449 }
 450
 451 static void tag_as_user_data(struct expression *expr)
 452 {
 453         struct symbol *type;
 454
 455         expr = strip_expr(expr);
 456
 457         type = get_type(expr);
 458         if (!type || type->type != SYM_PTR)
 459                 return;
 460         type = get_real_base_type(type);
 461         if (!type)
 462                 return;
 463         if (type == &void_ctype) {
 464                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 465                 return;
 466         }
 467         if (type->type == SYM_BASETYPE)
 468                 tag_base_type(expr);
 469         if (type->type == SYM_STRUCT) {
 470                 if (expr->type != EXPR_PREOP || expr->op != '&')
 471                         expr = deref_expression(expr);
 472                 tag_struct_members(type, expr);
 473         }
 474 }
 475
 476 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 477 {
 478         int param = PTR_INT(_param);
 479         struct expression *dest;
 480
 481         dest = get_argument_from_call_expr(expr->args, param);
 482         dest = strip_expr(dest);
 483         if (!dest)
 484                 return;
 485         tag_as_user_data(dest);
 486 }
 487
 488 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 489 {
 490         set_state_expr(my_id, expr->left, &user_data_set);
 491 }
 492
 493 static void match_caller_info(struct expression *expr)
 494 {
 495         struct expression *tmp;
 496         int i;
 497
 498         i = 0;
 499         FOR_EACH_PTR(expr->args, tmp) {
 500                 if (is_user_data(tmp))
 501                         sql_insert_caller_info(expr, USER_DATA, i, "$", "");
 502                 i++;
 503         } END_FOR_EACH_PTR(tmp);
 504 }
 505
 506 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 507 {
 508         if (sm->state == &capped)
 509                 return;
 510         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 511 }
 512
 513 static void returned_member_callback(int return_id, char *return_ranges, struct expression *expr, char *printed_name, struct smatch_state *state)
 514 {
 515         if (state == &capped)
 516                 return;
 517         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 518 }
 519
 520 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 521 {
 522         struct stree *stree;
 523         struct sm_state *tmp;
 524         int param;
 525         int user_data;
 526         const char *passed_or_new;
 527
 528         user_data = is_user_data(expr);
 529         if (user_data == PASSED_DATA) {
 530                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 531                                 -1, "$", "2");
 532         }
 533         if (user_data == SET_DATA) {
 534                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 535                                 -1, "$", "1");
 536         }
 537
 538         stree = __get_cur_stree();
 539
 540         FOR_EACH_MY_SM(my_id, stree, tmp) {
 541                 const char *param_name;
 542
 543                 param = get_param_num_from_sym(tmp->sym);
 544                 if (param < 0)
 545                         continue;
 546
 547                 if (is_capped_var_sym(tmp->name, tmp->sym))
 548                         continue;
 549                 /* ignore states that were already USER_DATA to begin with */
 550                 if (get_state_stree(get_start_states(), my_id, tmp->name, tmp->sym))
 551                         continue;
 552
 553                 param_name = get_param_name(tmp);
 554                 if (!param_name || strcmp(param_name, "$") == 0)
 555                         continue;
 556
 557                 if (slist_has_state(tmp->possible, &user_data_set))
 558                         passed_or_new = "1";
 559                 else if (slist_has_state(tmp->possible, &user_data_passed))
 560                         passed_or_new = "2";
 561                 else
 562                         continue;
 563
 564                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 565                                 param, param_name, passed_or_new);
 566         } END_FOR_EACH_SM(tmp);
 567 }
 568
 569 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 570 {
 571         char *name;
 572         struct symbol *sym;
 573
 574         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$") == 0) {
 575                 tag_as_user_data(expr->left);
 576                 return;
 577         }
 578
 579         name = return_state_to_var_sym(expr, param, key, &sym);
 580         if (!name || !sym)
 581                 goto free;
 582
 583         set_state(my_id, name, sym, &user_data_set);
 584 free:
 585         free_string(name);
 586 }
 587
 588 void check_user_data(int id)
 589 {
 590         int i;
 591
 592         if (option_project != PROJ_KERNEL)
 593                 return;
 594         my_id = id;
 595         select_caller_info_hook(set_called, INTERNAL);
 596         select_caller_info_hook(set_param_user_data, USER_DATA);
 597         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 598         add_hook(&match_condition, CONDITION_HOOK);
 599         add_hook(&match_assign, ASSIGNMENT_HOOK);
 600         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 601         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 602         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 603         add_function_assign_hook("memdup_user", &match_user_assign_function, NULL);
 604         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 605         for (i = 0; i < ARRAY_SIZE(kstr_funcs); i++)
 606                 add_function_hook(kstr_funcs[i], &match_user_copy, INT_PTR(2));
 607
 608         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 609         add_member_info_callback(my_id, struct_member_callback);
 610         add_returned_member_callback(my_id, returned_member_callback);
 611         add_split_return_callback(print_returned_user_data);
 612         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 613 }