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