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 state_list *my_slist)
  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_PTR(my_slist, sm) {
  74                 if (sm->sym == sym)
  75                         return 1;
  76         } END_FOR_EACH_PTR(sm);
  77         return 0;
  78 }
  79
  80 static int passes_user_data(struct expression *expr)
  81 {
  82         struct state_list *slist;
  83         struct expression *arg;
  84
  85         slist = get_all_states(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, slist))
  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 state_list *slist = 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         slist = get_all_states(my_id);
 208         FOR_EACH_PTR(slist, 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_PTR(tmp);
 219
 220 free:
 221         free_slist(&slist);
 222         free_string(name);
 223         return user;
 224 }
 225
 226 int is_user_data(struct expression *expr)
 227 {
 228         int user_data;
 229
 230         if (!expr)
 231                 return 0;
 232
 233         if (is_capped(expr))
 234                 return 0;
 235         if (in_container_of_macro(expr))
 236                 return 0;
 237
 238         user_data = is_user_macro(expr);
 239         if (user_data)
 240                 return user_data;
 241         user_data = is_user_function(expr);
 242         if (user_data)
 243                 return user_data;
 244         user_data = is_skb_data(expr);
 245         if (user_data)
 246                 return user_data;
 247
 248         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 249
 250         if (expr->type == EXPR_BINOP) {
 251                 user_data = is_user_data(expr->left);
 252                 if (user_data)
 253                         return user_data;
 254                 if (is_array(expr))
 255                         return 0;
 256                 user_data = is_user_data(expr->right);
 257                 if (user_data)
 258                         return user_data;
 259                 return 0;
 260         }
 261         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 262                 expr = strip_expr(expr->unop);
 263
 264         return is_user_data_state(expr);
 265 }
 266
 267 int is_capped_user_data(struct expression *expr)
 268 {
 269         struct sm_state *sm;
 270
 271         sm = get_sm_state_expr(my_id, expr);
 272         if (!sm)
 273                 return 0;
 274         if (slist_has_state(sm->possible, &capped))
 275                 return 1;
 276         return 0;
 277 }
 278
 279 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 280 {
 281         char fullname[256];
 282
 283         /* sanity check.  this should always be true. */
 284         if (strncmp(key, "$$", 2) != 0)
 285                 return;
 286         snprintf(fullname, 256, "%s%s", name, key + 2);
 287         set_state(my_id, fullname, sym, &user_data_passed);
 288 }
 289
 290 static void match_syscall_definition(struct symbol *sym)
 291 {
 292         struct symbol *arg;
 293         char *macro;
 294
 295         macro = get_macro_name(sym->pos);
 296         if (!macro)
 297                 return;
 298         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 299             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 300                 return;
 301
 302         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 303                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 304         } END_FOR_EACH_PTR(arg);
 305 }
 306
 307 static void match_condition(struct expression *expr)
 308 {
 309         switch (expr->op) {
 310         case '<':
 311         case SPECIAL_LTE:
 312         case SPECIAL_UNSIGNED_LT:
 313         case SPECIAL_UNSIGNED_LTE:
 314                 if (is_user_data(expr->left))
 315                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 316                 if (is_user_data(expr->right))
 317                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 318                 break;
 319         case '>':
 320         case SPECIAL_GTE:
 321         case SPECIAL_UNSIGNED_GT:
 322         case SPECIAL_UNSIGNED_GTE:
 323                 if (is_user_data(expr->right))
 324                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 325                 if (is_user_data(expr->left))
 326                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 327                 break;
 328         case SPECIAL_EQUAL:
 329                 if (is_user_data(expr->left))
 330                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 331                 if (is_user_data(expr->right))
 332                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 333                 break;
 334         case SPECIAL_NOTEQUAL:
 335                 if (is_user_data(expr->left))
 336                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 337                 if (is_user_data(expr->right))
 338                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 339                 break;
 340         default:
 341                 return;
 342         }
 343 }
 344
 345 static int handle_get_user(struct expression *expr)
 346 {
 347         char *name;
 348         int ret = 0;
 349
 350         name = get_macro_name(expr->pos);
 351         if (!name || strcmp(name, "get_user") != 0)
 352                 return 0;
 353
 354         name = expr_to_var(expr->right);
 355         if (!name || strcmp(name, "__val_gu") != 0)
 356                 goto free;
 357         set_state_expr(my_id, expr->left, &user_data_set);
 358         ret = 1;
 359 free:
 360         free_string(name);
 361         return ret;
 362 }
 363
 364 static void match_assign(struct expression *expr)
 365 {
 366         int user_data;
 367
 368         if (handle_get_user(expr))
 369                 return;
 370
 371         user_data = is_user_data(expr->right);
 372         if (user_data == PASSED_DATA)
 373                 set_state_expr(my_id, expr->left, &user_data_passed);
 374         else if (user_data == SET_DATA)
 375                 set_state_expr(my_id, expr->left, &user_data_set);
 376         else if (get_state_expr(my_id, expr->left))
 377                 set_state_expr(my_id, expr->left, &capped);
 378 }
 379
 380 static void tag_struct_members(struct symbol *type, struct expression *expr)
 381 {
 382         struct symbol *tmp;
 383         struct expression *member;
 384         int op = '*';
 385
 386         if (expr->type == EXPR_PREOP && expr->op == '&') {
 387                 expr = strip_expr(expr->unop);
 388                 op = '.';
 389         }
 390
 391         FOR_EACH_PTR(type->symbol_list, tmp) {
 392                 if (!tmp->ident)
 393                         continue;
 394                 member = member_expression(expr, op, tmp->ident);
 395                 set_state_expr(my_id, member, &user_data_set);
 396         } END_FOR_EACH_PTR(tmp);
 397 }
 398
 399 static void tag_base_type(struct expression *expr)
 400 {
 401         if (expr->type == EXPR_PREOP && expr->op == '&')
 402                 expr = strip_expr(expr->unop);
 403         else
 404                 expr = deref_expression(expr);
 405         set_state_expr(my_id, expr, &user_data_set);
 406 }
 407
 408 static void tag_as_user_data(struct expression *expr)
 409 {
 410         struct symbol *type;
 411
 412         expr = strip_expr(expr);
 413
 414         type = get_type(expr);
 415         if (!type || type->type != SYM_PTR)
 416                 return;
 417         type = get_real_base_type(type);
 418         if (!type)
 419                 return;
 420         if (type == &void_ctype) {
 421                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 422                 return;
 423         }
 424         if (type->type == SYM_BASETYPE)
 425                 tag_base_type(expr);
 426         if (type->type == SYM_STRUCT) {
 427                 if (expr->type != EXPR_PREOP || expr->op != '&')
 428                         expr = deref_expression(expr);
 429                 tag_struct_members(type, expr);
 430         }
 431 }
 432
 433 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 434 {
 435         int param = PTR_INT(_param);
 436         struct expression *dest;
 437
 438         dest = get_argument_from_call_expr(expr->args, param);
 439         dest = strip_expr(dest);
 440         if (!dest)
 441                 return;
 442         tag_as_user_data(dest);
 443 }
 444
 445 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 446 {
 447         set_state_expr(my_id, expr->left, &user_data_set);
 448 }
 449
 450 static void match_caller_info(struct expression *expr)
 451 {
 452         struct expression *tmp;
 453         int i;
 454
 455         i = 0;
 456         FOR_EACH_PTR(expr->args, tmp) {
 457                 if (is_user_data(tmp))
 458                         sql_insert_caller_info(expr, USER_DATA, i, "$$", "");
 459                 i++;
 460         } END_FOR_EACH_PTR(tmp);
 461 }
 462
 463 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 464 {
 465         if (state == &capped)
 466                 return;
 467         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 468 }
 469
 470 static void returned_member_callback(int return_id, char *return_ranges, char *printed_name, struct smatch_state *state)
 471 {
 472         if (state == &capped)
 473                 return;
 474         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 475 }
 476
 477 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 478 {
 479         struct state_list *my_slist;
 480         struct sm_state *tmp;
 481         int param;
 482         int user_data;
 483         const char *passed_or_new;
 484
 485         user_data = is_user_data(expr);
 486         if (user_data == PASSED_DATA) {
 487                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 488                                 -1, "$$", "2");
 489         }
 490         if (user_data == SET_DATA) {
 491                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 492                                 -1, "$$", "1");
 493         }
 494
 495         my_slist = get_all_states(my_id);
 496
 497         FOR_EACH_PTR(my_slist, tmp) {
 498                 const char *param_name;
 499
 500                 param = get_param_num_from_sym(tmp->sym);
 501                 if (param < 0)
 502                         continue;
 503
 504                 if (is_capped_var_sym(tmp->name, tmp->sym))
 505                         continue;
 506                 /* ignore states that were already USER_DATA to begin with */
 507                 if (get_state_slist(get_start_states(), my_id, tmp->name, tmp->sym))
 508                         continue;
 509
 510                 param_name = get_param_name(tmp);
 511                 if (!param_name || strcmp(param_name, "$$") == 0)
 512                         continue;
 513
 514                 if (slist_has_state(tmp->possible, &user_data_set))
 515                         passed_or_new = "1";
 516                 else if (slist_has_state(tmp->possible, &user_data_passed))
 517                         passed_or_new = "2";
 518                 else
 519                         continue;
 520
 521                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 522                                 param, param_name, passed_or_new);
 523         } END_FOR_EACH_PTR(tmp);
 524
 525         free_slist(&my_slist);
 526 }
 527
 528 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 529 {
 530         char *name;
 531         struct symbol *sym;
 532
 533         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$$") == 0) {
 534                 tag_as_user_data(expr->left);
 535                 return;
 536         }
 537
 538         name = return_state_to_var_sym(expr, param, key, &sym);
 539         if (!name || !sym)
 540                 goto free;
 541
 542         set_state(my_id, name, sym, &user_data_set);
 543 free:
 544         free_string(name);
 545 }
 546
 547 void check_user_data(int id)
 548 {
 549         if (option_project != PROJ_KERNEL)
 550                 return;
 551         my_id = id;
 552         select_caller_info_hook(set_param_user_data, USER_DATA);
 553         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 554         add_hook(&match_condition, CONDITION_HOOK);
 555         add_hook(&match_assign, ASSIGNMENT_HOOK);
 556         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 557         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 558         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 559         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 560
 561         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 562         add_member_info_callback(my_id, struct_member_callback);
 563         add_returned_member_callback(my_id, returned_member_callback);
 564         add_split_return_callback(print_returned_user_data);
 565         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 566 }