check_user_data.c

   1 /*
   2  * smatch/check_user_data.c
   3  *
   4  * Copyright (C) 2011 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * There are a couple checks that try to see if a variable
  12  * comes from the user.  It would be better to unify them
  13  * into one place.  Also it we should follow the data down
  14  * the call paths.  Hence this file.
  15  */
  16
  17 #include "smatch.h"
  18 #include "smatch_slist.h"
  19 #include "smatch_extra.h"
  20
  21 static int my_id;
  22
  23 STATE(capped);
  24 STATE(user_data_passed);
  25 STATE(user_data_set);
  26
  27 enum {
  28         SET_DATA = 1,
  29         PASSED_DATA = 2,
  30 };
  31
  32 int is_user_macro(struct expression *expr)
  33 {
  34         char *macro;
  35         struct range_list *rl;
  36
  37         macro = get_macro_name(expr->pos);
  38
  39         if (!macro)
  40                 return 0;
  41         if (get_implied_rl(expr, &rl) && !is_whole_rl(rl))
  42                 return 0;
  43         if (strcmp(macro, "ntohl") == 0)
  44                 return SET_DATA;
  45         if (strcmp(macro, "ntohs") == 0)
  46                 return SET_DATA;
  47         return 0;
  48 }
  49
  50 static int has_user_data_state(struct expression *expr, struct state_list *my_slist)
  51 {
  52         struct sm_state *sm;
  53         struct symbol *sym;
  54         char *name;
  55
  56         expr = strip_expr(expr);
  57         if (expr->type == EXPR_PREOP && expr->op == '&')
  58                 expr = strip_expr(expr->unop);
  59
  60         name = expr_to_str_sym(expr, &sym);
  61         free_string(name);
  62         if (!sym)
  63                 return 1;
  64
  65         FOR_EACH_PTR(my_slist, sm) {
  66                 if (sm->sym == sym)
  67                         return 1;
  68         } END_FOR_EACH_PTR(sm);
  69         return 0;
  70 }
  71
  72 static int passes_user_data(struct expression *expr)
  73 {
  74         struct state_list *slist;
  75         struct expression *arg;
  76
  77         slist = get_all_states(my_id);
  78         FOR_EACH_PTR(expr->args, arg) {
  79                 if (is_user_data(arg))
  80                         return 1;
  81                 if (has_user_data_state(arg, slist))
  82                         return 1;
  83         } END_FOR_EACH_PTR(arg);
  84
  85         return 0;
  86 }
  87
  88 static struct expression *db_expr;
  89 static int db_user_data;
  90 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
  91 {
  92         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
  93                 return 0;
  94         db_user_data = 1;
  95         return 0;
  96 }
  97
  98 static int is_user_fn_db(struct expression *expr)
  99 {
 100         struct symbol *sym;
 101         static char sql_filter[1024];
 102
 103         if (is_fake_call(expr))
 104                 return 0;
 105         if (expr->fn->type != EXPR_SYMBOL)
 106                 return 0;
 107         sym = expr->fn->symbol;
 108         if (!sym)
 109                 return 0;
 110
 111         if (sym->ctype.modifiers & MOD_STATIC) {
 112                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 113                          get_filename(), sym->ident->name);
 114         } else {
 115                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 116                                 sym->ident->name);
 117         }
 118
 119         db_expr = expr;
 120         db_user_data = 0;
 121         run_sql(db_user_data_callback,
 122                 "select value from return_states where type=%d and parameter = -1 and key = '$$' and %s",
 123                 USER_DATA, sql_filter);
 124         return db_user_data;
 125 }
 126
 127 static int is_user_function(struct expression *expr)
 128 {
 129         if (expr->type != EXPR_CALL)
 130                 return 0;
 131         return is_user_fn_db(expr);
 132 }
 133
 134 static int is_skb_data(struct expression *expr)
 135 {
 136         struct symbol *sym;
 137         char *name;
 138         int len;
 139         int ret = 0;
 140
 141         name = expr_to_var_sym(expr, &sym);
 142         if (!name || !sym)
 143                 goto free;
 144
 145         sym = get_base_type(sym);
 146         if (!sym || sym->type != SYM_PTR)
 147                 goto free;
 148         sym = get_base_type(sym);
 149         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 150                 goto free;
 151         if (strcmp(sym->ident->name, "sk_buff") != 0)
 152                 goto free;
 153
 154         len = strlen(name);
 155         if (len < 6)
 156                 goto free;
 157         if (strcmp(name + len - 6, "->data") == 0)
 158                 ret = SET_DATA;
 159
 160 free:
 161         free_string(name);
 162         return ret;
 163 }
 164
 165 static int in_container_of_macro(struct expression *expr)
 166 {
 167         char *macro;
 168
 169         macro = get_macro_name(expr->pos);
 170
 171         if (!macro)
 172                 return 0;
 173         if (strcmp(macro, "container_of") == 0)
 174                 return 1;
 175         return 0;
 176 }
 177
 178 static int is_user_data_state(struct expression *expr)
 179 {
 180         struct state_list *slist = NULL;
 181         struct sm_state *tmp;
 182         struct symbol *sym;
 183         char *name;
 184         int user = 0;
 185
 186         tmp = get_sm_state_expr(my_id, expr);
 187         if (tmp) {
 188                 if (slist_has_state(tmp->possible, &user_data_set))
 189                         return SET_DATA;
 190                 if (slist_has_state(tmp->possible, &user_data_passed))
 191                         return PASSED_DATA;
 192                 return 0;
 193         }
 194
 195         name = expr_to_str_sym(expr, &sym);
 196         if (!name || !sym)
 197                 goto free;
 198
 199         slist = get_all_states(my_id);
 200         FOR_EACH_PTR(slist, tmp) {
 201                 if (tmp->sym != sym)
 202                         continue;
 203                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 204                         if (slist_has_state(tmp->possible, &user_data_set))
 205                                 user = SET_DATA;
 206                         else if (slist_has_state(tmp->possible, &user_data_passed))
 207                                 user = PASSED_DATA;
 208                         goto free;
 209                 }
 210         } END_FOR_EACH_PTR(tmp);
 211
 212 free:
 213         free_slist(&slist);
 214         free_string(name);
 215         return user;
 216 }
 217
 218 int is_user_data(struct expression *expr)
 219 {
 220         int user_data;
 221
 222         if (!expr)
 223                 return 0;
 224
 225         if (is_capped(expr))
 226                 return 0;
 227         if (in_container_of_macro(expr))
 228                 return 0;
 229
 230         user_data = is_user_macro(expr);
 231         if (user_data)
 232                 return user_data;
 233         user_data = is_user_function(expr);
 234         if (user_data)
 235                 return user_data;
 236         user_data = is_skb_data(expr);
 237         if (user_data)
 238                 return user_data;
 239
 240         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 241
 242         if (expr->type == EXPR_BINOP) {
 243                 user_data = is_user_data(expr->left);
 244                 if (user_data)
 245                         return user_data;
 246                 if (is_array(expr))
 247                         return 0;
 248                 user_data = is_user_data(expr->right);
 249                 if (user_data)
 250                         return user_data;
 251                 return 0;
 252         }
 253         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 254                 expr = strip_expr(expr->unop);
 255
 256         return is_user_data_state(expr);
 257 }
 258
 259 int is_capped_user_data(struct expression *expr)
 260 {
 261         struct sm_state *sm;
 262
 263         sm = get_sm_state_expr(my_id, expr);
 264         if (!sm)
 265                 return 0;
 266         if (slist_has_state(sm->possible, &capped))
 267                 return 1;
 268         return 0;
 269 }
 270
 271 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 272 {
 273         char fullname[256];
 274
 275         /* sanity check.  this should always be true. */
 276         if (strncmp(key, "$$", 2) != 0)
 277                 return;
 278         snprintf(fullname, 256, "%s%s", name, key + 2);
 279         set_state(my_id, fullname, sym, &user_data_passed);
 280 }
 281
 282 static void match_syscall_definition(struct symbol *sym)
 283 {
 284         struct symbol *arg;
 285         char *macro;
 286
 287         macro = get_macro_name(sym->pos);
 288         if (!macro)
 289                 return;
 290         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 291             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 292                 return;
 293
 294         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 295                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 296         } END_FOR_EACH_PTR(arg);
 297 }
 298
 299 static void match_condition(struct expression *expr)
 300 {
 301         switch (expr->op) {
 302         case '<':
 303         case SPECIAL_LTE:
 304         case SPECIAL_UNSIGNED_LT:
 305         case SPECIAL_UNSIGNED_LTE:
 306                 if (is_user_data(expr->left))
 307                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 308                 if (is_user_data(expr->right))
 309                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 310                 break;
 311         case '>':
 312         case SPECIAL_GTE:
 313         case SPECIAL_UNSIGNED_GT:
 314         case SPECIAL_UNSIGNED_GTE:
 315                 if (is_user_data(expr->right))
 316                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 317                 if (is_user_data(expr->left))
 318                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 319                 break;
 320         case SPECIAL_EQUAL:
 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, &capped, NULL);
 325                 break;
 326         case SPECIAL_NOTEQUAL:
 327                 if (is_user_data(expr->left))
 328                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 329                 if (is_user_data(expr->right))
 330                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 331                 break;
 332         default:
 333                 return;
 334         }
 335 }
 336
 337 static void set_capped(struct sm_state *sm, struct expression *mod_expr)
 338 {
 339         set_state(my_id, sm->name, sm->sym, &capped);
 340 }
 341
 342 static int handle_get_user(struct expression *expr)
 343 {
 344         char *name;
 345         int ret = 0;
 346
 347         name = get_macro_name(expr->pos);
 348         if (!name || strcmp(name, "get_user") != 0)
 349                 return 0;
 350
 351         name = expr_to_var(expr->right);
 352         if (!name || strcmp(name, "__val_gu") != 0)
 353                 goto free;
 354         set_state_expr(my_id, expr->left, &user_data_set);
 355         ret = 1;
 356 free:
 357         free_string(name);
 358         return ret;
 359 }
 360
 361 static void match_assign(struct expression *expr)
 362 {
 363         int user_data;
 364
 365         if (handle_get_user(expr))
 366                 return;
 367
 368         user_data = is_user_data(expr->right);
 369         if (user_data == PASSED_DATA)
 370                 set_state_expr(my_id, expr->left, &user_data_passed);
 371         else if (user_data == SET_DATA)
 372                 set_state_expr(my_id, expr->left, &user_data_set);
 373 }
 374
 375 static void tag_struct_members(struct symbol *type, struct expression *expr)
 376 {
 377         struct symbol *tmp;
 378         struct expression *member;
 379         int op = '*';
 380
 381         if (expr->type == EXPR_PREOP && expr->op == '&') {
 382                 expr = strip_expr(expr->unop);
 383                 op = '.';
 384         }
 385
 386         FOR_EACH_PTR(type->symbol_list, tmp) {
 387                 if (!tmp->ident)
 388                         continue;
 389                 member = member_expression(expr, op, tmp->ident);
 390                 set_state_expr(my_id, member, &user_data_set);
 391         } END_FOR_EACH_PTR(tmp);
 392 }
 393
 394 static void tag_base_type(struct expression *expr)
 395 {
 396         if (expr->type == EXPR_PREOP && expr->op == '&')
 397                 expr = strip_expr(expr->unop);
 398         else
 399                 expr = deref_expression(expr);
 400         set_state_expr(my_id, expr, &user_data_set);
 401 }
 402
 403 static void tag_as_user_data(struct expression *expr)
 404 {
 405         struct symbol *type;
 406
 407         expr = strip_expr(expr);
 408
 409         type = get_type(expr);
 410         if (!type || type->type != SYM_PTR)
 411                 return;
 412         type = get_real_base_type(type);
 413         if (!type)
 414                 return;
 415         if (type == &void_ctype) {
 416                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 417                 return;
 418         }
 419         if (type->type == SYM_BASETYPE)
 420                 tag_base_type(expr);
 421         if (type->type == SYM_STRUCT) {
 422                 if (expr->type != EXPR_PREOP || expr->op != '&')
 423                         expr = deref_expression(expr);
 424                 tag_struct_members(type, expr);
 425         }
 426 }
 427
 428 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 429 {
 430         int param = PTR_INT(_param);
 431         struct expression *dest;
 432
 433         dest = get_argument_from_call_expr(expr->args, param);
 434         dest = strip_expr(dest);
 435         if (!dest)
 436                 return;
 437         tag_as_user_data(dest);
 438 }
 439
 440 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 441 {
 442         set_state_expr(my_id, expr->left, &user_data_set);
 443 }
 444
 445 static void match_macro_assign(const char *fn, struct expression *expr, void *_bits)
 446 {
 447         int bits;
 448
 449         bits = nr_bits(expr->left);
 450         if (!bits)
 451                 return;
 452         if (bits > nr_bits(expr->right))
 453                 return;
 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, "$$", "");
 466                 i++;
 467         } END_FOR_EACH_PTR(tmp);
 468 }
 469
 470 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 471 {
 472         if (state == &capped)
 473                 return;
 474         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 475 }
 476
 477 static void returned_member_callback(int return_id, char *return_ranges, char *printed_name, struct smatch_state *state)
 478 {
 479         if (state == &capped)
 480                 return;
 481         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 482 }
 483
 484 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 485 {
 486         struct state_list *my_slist;
 487         struct sm_state *tmp;
 488         int param;
 489         int user_data;
 490         const char *passed_or_new;
 491
 492         user_data = is_user_data(expr);
 493         if (user_data == PASSED_DATA) {
 494                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 495                                 -1, "$$", "2");
 496         }
 497         if (user_data == SET_DATA) {
 498                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 499                                 -1, "$$", "1");
 500         }
 501
 502         my_slist = get_all_states(my_id);
 503
 504         FOR_EACH_PTR(my_slist, tmp) {
 505                 const char *param_name;
 506
 507                 param = get_param_num_from_sym(tmp->sym);
 508                 if (param < 0)
 509                         continue;
 510
 511                 if (is_capped_var_sym(tmp->name, tmp->sym))
 512                         continue;
 513                 /* ignore states that were already USER_DATA to begin with */
 514                 if (get_state_slist(get_start_states(), my_id, tmp->name, tmp->sym))
 515                         continue;
 516
 517                 param_name = get_param_name(tmp);
 518                 if (!param_name)
 519                         return;
 520
 521                 if (slist_has_state(tmp->possible, &user_data_set))
 522                         passed_or_new = "1";
 523                 else if (slist_has_state(tmp->possible, &user_data_passed))
 524                         passed_or_new = "2";
 525                 else
 526                         continue;
 527
 528                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 529                                 param, param_name, passed_or_new);
 530         } END_FOR_EACH_PTR(tmp);
 531
 532         free_slist(&my_slist);
 533 }
 534
 535 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 536 {
 537         char *name;
 538         struct symbol *sym;
 539
 540         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$$") == 0) {
 541                 tag_as_user_data(expr->left);
 542                 return;
 543         }
 544
 545         name = return_state_to_var_sym(expr, param, key, &sym);
 546         if (!name || !sym)
 547                 goto free;
 548
 549         set_state(my_id, name, sym, &user_data_set);
 550 free:
 551         free_string(name);
 552 }
 553
 554 void check_user_data(int id)
 555 {
 556         if (option_project != PROJ_KERNEL)
 557                 return;
 558         my_id = id;
 559         select_caller_info_hook(set_param_user_data, USER_DATA);
 560         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 561         add_hook(&match_condition, CONDITION_HOOK);
 562         add_hook(&match_assign, ASSIGNMENT_HOOK);
 563         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 564         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 565         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 566         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 567
 568         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 569         add_member_info_callback(my_id, struct_member_callback);
 570         add_returned_member_callback(my_id, returned_member_callback);
 571         add_split_return_callback(print_returned_user_data);
 572         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 573
 574         add_modification_hook(my_id, &set_capped);
 575
 576         add_macro_assign_hook("ntohl", &match_macro_assign, NULL);
 577         add_macro_assign_hook("ntohs", &match_macro_assign, NULL);
 578 }