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 void tag_as_user_data(struct expression *expr);
  22
  23 static int my_id;
  24
  25 STATE(capped);
  26 STATE(user_data_passed);
  27 STATE(user_data_set);
  28
  29 enum {
  30         SET_DATA = 1,
  31         PASSED_DATA = 2,
  32 };
  33
  34 int is_user_macro(struct expression *expr)
  35 {
  36         char *macro;
  37         struct range_list *rl;
  38
  39         macro = get_macro_name(expr->pos);
  40
  41         if (!macro)
  42                 return 0;
  43         if (get_implied_rl(expr, &rl) && !is_whole_rl(rl))
  44                 return 0;
  45         if (strcmp(macro, "ntohl") == 0)
  46                 return SET_DATA;
  47         if (strcmp(macro, "ntohs") == 0)
  48                 return SET_DATA;
  49         return 0;
  50 }
  51
  52 static int has_user_data_state(struct expression *expr, struct state_list *my_slist)
  53 {
  54         struct sm_state *sm;
  55         struct symbol *sym;
  56         char *name;
  57
  58         expr = strip_expr(expr);
  59         if (expr->type == EXPR_PREOP && expr->op == '&')
  60                 expr = strip_expr(expr->unop);
  61
  62         name = expr_to_str_sym(expr, &sym);
  63         free_string(name);
  64         if (!sym)
  65                 return 1;
  66
  67         FOR_EACH_PTR(my_slist, sm) {
  68                 if (sm->sym == sym)
  69                         return 1;
  70         } END_FOR_EACH_PTR(sm);
  71         return 0;
  72 }
  73
  74 static int passes_user_data(struct expression *expr)
  75 {
  76         struct state_list *slist;
  77         struct expression *arg;
  78
  79         slist = get_all_states(my_id);
  80         FOR_EACH_PTR(expr->args, arg) {
  81                 if (is_user_data(arg))
  82                         return 1;
  83                 if (has_user_data_state(arg, slist))
  84                         return 1;
  85         } END_FOR_EACH_PTR(arg);
  86
  87         return 0;
  88 }
  89
  90 static struct expression *db_expr;
  91 static int db_user_data;
  92 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
  93 {
  94         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
  95                 return 0;
  96         db_user_data = 1;
  97         return 0;
  98 }
  99
 100 static int is_user_fn_db(struct expression *expr)
 101 {
 102         struct symbol *sym;
 103         static char sql_filter[1024];
 104
 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         if (sym_name_is("kmemdup_user", expr->fn))
 132                 return SET_DATA;
 133         return is_user_fn_db(expr);
 134 }
 135
 136 static int is_skb_data(struct expression *expr)
 137 {
 138         struct symbol *sym;
 139         char *name;
 140         int len;
 141         int ret = 0;
 142
 143         name = expr_to_var_sym(expr, &sym);
 144         if (!name || !sym)
 145                 goto free;
 146
 147         sym = get_base_type(sym);
 148         if (!sym || sym->type != SYM_PTR)
 149                 goto free;
 150         sym = get_base_type(sym);
 151         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 152                 goto free;
 153         if (strcmp(sym->ident->name, "sk_buff") != 0)
 154                 goto free;
 155
 156         len = strlen(name);
 157         if (len < 6)
 158                 goto free;
 159         if (strcmp(name + len - 6, "->data") == 0)
 160                 ret = SET_DATA;
 161
 162 free:
 163         free_string(name);
 164         return ret;
 165 }
 166
 167 static int in_container_of_macro(struct expression *expr)
 168 {
 169         char *macro;
 170
 171         macro = get_macro_name(expr->pos);
 172
 173         if (!macro)
 174                 return 0;
 175         if (strcmp(macro, "container_of") == 0)
 176                 return 1;
 177         return 0;
 178 }
 179
 180 static int is_user_data_state(struct expression *expr)
 181 {
 182         struct state_list *slist = NULL;
 183         struct sm_state *tmp;
 184         struct symbol *sym;
 185         char *name;
 186         int user = 0;
 187
 188         tmp = get_sm_state_expr(my_id, expr);
 189         if (tmp) {
 190                 if (slist_has_state(tmp->possible, &user_data_set))
 191                         return SET_DATA;
 192                 if (slist_has_state(tmp->possible, &user_data_passed))
 193                         return PASSED_DATA;
 194                 return 0;
 195         }
 196
 197         name = expr_to_str_sym(expr, &sym);
 198         if (!name || !sym)
 199                 goto free;
 200
 201         slist = get_all_states(my_id);
 202         FOR_EACH_PTR(slist, tmp) {
 203                 if (tmp->sym != sym)
 204                         continue;
 205                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 206                         if (slist_has_state(tmp->possible, &user_data_set))
 207                                 user = SET_DATA;
 208                         else if (slist_has_state(tmp->possible, &user_data_passed))
 209                                 user = PASSED_DATA;
 210                         goto free;
 211                 }
 212         } END_FOR_EACH_PTR(tmp);
 213
 214 free:
 215         free_slist(&slist);
 216         free_string(name);
 217         return user;
 218 }
 219
 220 int is_user_data(struct expression *expr)
 221 {
 222         int user_data;
 223
 224         if (!expr)
 225                 return 0;
 226
 227         if (is_capped(expr))
 228                 return 0;
 229         if (in_container_of_macro(expr))
 230                 return 0;
 231
 232         user_data = is_user_macro(expr);
 233         if (user_data)
 234                 return user_data;
 235         user_data = is_user_function(expr);
 236         if (user_data)
 237                 return user_data;
 238         user_data = is_skb_data(expr);
 239         if (user_data)
 240                 return user_data;
 241
 242         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 243
 244         if (expr->type == EXPR_BINOP) {
 245                 user_data = is_user_data(expr->left);
 246                 if (user_data)
 247                         return user_data;
 248                 if (is_array(expr))
 249                         return 0;
 250                 user_data = is_user_data(expr->right);
 251                 if (user_data)
 252                         return user_data;
 253                 return 0;
 254         }
 255         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 256                 expr = strip_expr(expr->unop);
 257
 258         return is_user_data_state(expr);
 259 }
 260
 261 int is_capped_user_data(struct expression *expr)
 262 {
 263         struct sm_state *sm;
 264
 265         sm = get_sm_state_expr(my_id, expr);
 266         if (!sm)
 267                 return 0;
 268         if (slist_has_state(sm->possible, &capped))
 269                 return 1;
 270         return 0;
 271 }
 272
 273 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 274 {
 275         char fullname[256];
 276
 277         /* sanity check.  this should always be true. */
 278         if (strncmp(key, "$$", 2) != 0)
 279                 return;
 280         snprintf(fullname, 256, "%s%s", name, key + 2);
 281         set_state(my_id, fullname, sym, &user_data_passed);
 282 }
 283
 284 static void match_syscall_definition(struct symbol *sym)
 285 {
 286         struct symbol *arg;
 287         char *macro;
 288
 289         macro = get_macro_name(sym->pos);
 290         if (!macro)
 291                 return;
 292         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 293             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 294                 return;
 295
 296         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 297                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 298         } END_FOR_EACH_PTR(arg);
 299 }
 300
 301 static void match_condition(struct expression *expr)
 302 {
 303         switch (expr->op) {
 304         case '<':
 305         case SPECIAL_LTE:
 306         case SPECIAL_UNSIGNED_LT:
 307         case SPECIAL_UNSIGNED_LTE:
 308                 if (is_user_data(expr->left))
 309                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 310                 if (is_user_data(expr->right))
 311                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 312                 break;
 313         case '>':
 314         case SPECIAL_GTE:
 315         case SPECIAL_UNSIGNED_GT:
 316         case SPECIAL_UNSIGNED_GTE:
 317                 if (is_user_data(expr->right))
 318                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 319                 if (is_user_data(expr->left))
 320                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 321                 break;
 322         case SPECIAL_EQUAL:
 323                 if (is_user_data(expr->left))
 324                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 325                 if (is_user_data(expr->right))
 326                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 327                 break;
 328         case SPECIAL_NOTEQUAL:
 329                 if (is_user_data(expr->left))
 330                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 331                 if (is_user_data(expr->right))
 332                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 333                 break;
 334         default:
 335                 return;
 336         }
 337 }
 338
 339 static void set_capped(struct sm_state *sm, struct expression *mod_expr)
 340 {
 341         set_state(my_id, sm->name, sm->sym, &capped);
 342 }
 343
 344 static void match_normal_assign(struct expression *expr)
 345 {
 346         int user_data;
 347
 348         user_data = is_user_data(expr->right);
 349         if (user_data == PASSED_DATA)
 350                 set_state_expr(my_id, expr->left, &user_data_passed);
 351         if (user_data == SET_DATA)
 352                 set_state_expr(my_id, expr->left, &user_data_set);
 353 }
 354
 355 static void match_assign(struct expression *expr)
 356 {
 357         char *name;
 358
 359         name = get_macro_name(expr->pos);
 360         if (!name || strcmp(name, "get_user") != 0) {
 361                 match_normal_assign(expr);
 362                 return;
 363         }
 364         name = expr_to_var(expr->right);
 365         if (!name || strcmp(name, "__val_gu") != 0)
 366                 goto free;
 367         set_state_expr(my_id, expr->left, &user_data_set);
 368 free:
 369         free_string(name);
 370 }
 371
 372 static void tag_struct_members(struct symbol *type, struct expression *expr)
 373 {
 374         struct symbol *tmp;
 375         struct expression *member;
 376         int op = '*';
 377
 378         if (expr->type == EXPR_PREOP && expr->op == '&') {
 379                 expr = strip_expr(expr->unop);
 380                 op = '.';
 381         }
 382
 383         FOR_EACH_PTR(type->symbol_list, tmp) {
 384                 if (!tmp->ident)
 385                         continue;
 386                 member = member_expression(expr, op, tmp->ident);
 387                 set_state_expr(my_id, member, &user_data_set);
 388         } END_FOR_EACH_PTR(tmp);
 389 }
 390
 391 static void tag_base_type(struct expression *expr)
 392 {
 393         if (expr->type == EXPR_PREOP && expr->op == '&')
 394                 expr = strip_expr(expr->unop);
 395         else
 396                 expr = deref_expression(expr);
 397         set_state_expr(my_id, expr, &user_data_set);
 398 }
 399
 400 void tag_as_user_data(struct expression *expr)
 401 {
 402         struct symbol *type;
 403
 404         expr = strip_expr(expr);
 405
 406         type = get_type(expr);
 407         if (!type || type->type != SYM_PTR)
 408                 return;
 409         type = get_real_base_type(type);
 410         if (!type)
 411                 return;
 412         if (type == &void_ctype) {
 413                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 414                 return;
 415         }
 416         if (type->type == SYM_BASETYPE)
 417                 tag_base_type(expr);
 418         if (type->type == SYM_STRUCT) {
 419                 if (expr->type != EXPR_PREOP || expr->op != '&')
 420                         expr = deref_expression(expr);
 421                 tag_struct_members(type, expr);
 422         }
 423 }
 424
 425 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 426 {
 427         int param = PTR_INT(_param);
 428         struct expression *dest;
 429
 430         dest = get_argument_from_call_expr(expr->args, param);
 431         dest = strip_expr(dest);
 432         if (!dest)
 433                 return;
 434         tag_as_user_data(dest);
 435 }
 436
 437 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 438 {
 439         set_state_expr(my_id, expr->left, &user_data_set);
 440 }
 441
 442 static void match_macro_assign(const char *fn, struct expression *expr, void *_bits)
 443 {
 444         int bits;
 445
 446         bits = nr_bits(expr->left);
 447         if (!bits)
 448                 return;
 449         if (bits > nr_bits(expr->right))
 450                 return;
 451         set_state_expr(my_id, expr->left, &user_data_set);
 452 }
 453
 454 static void match_caller_info(struct expression *expr)
 455 {
 456         struct expression *tmp;
 457         int i;
 458
 459         i = 0;
 460         FOR_EACH_PTR(expr->args, tmp) {
 461                 if (is_user_data(tmp))
 462                         sql_insert_caller_info(expr, USER_DATA, i, "$$", "");
 463                 i++;
 464         } END_FOR_EACH_PTR(tmp);
 465 }
 466
 467 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 468 {
 469         if (state == &capped)
 470                 return;
 471         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 472 }
 473
 474 static void returned_member_callback(int return_id, char *return_ranges, char *printed_name, struct smatch_state *state)
 475 {
 476         if (state == &capped)
 477                 return;
 478         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 479 }
 480
 481 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 482 {
 483         struct state_list *my_slist;
 484         struct sm_state *tmp;
 485         int param;
 486         int user_data;
 487         const char *passed_or_new;
 488
 489         user_data = is_user_data(expr);
 490         if (user_data == PASSED_DATA) {
 491                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 492                                 -1, "$$", "2");
 493         }
 494         if (user_data == SET_DATA) {
 495                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 496                                 -1, "$$", "1");
 497         }
 498
 499         my_slist = get_all_states(my_id);
 500
 501         FOR_EACH_PTR(my_slist, tmp) {
 502                 const char *param_name;
 503
 504                 param = get_param_num_from_sym(tmp->sym);
 505                 if (param < 0)
 506                         continue;
 507
 508                 if (is_capped_var_sym(tmp->name, tmp->sym))
 509                         continue;
 510                 /* ignore states that were already USER_DATA to begin with */
 511                 if (get_state_slist(get_start_states(), my_id, tmp->name, tmp->sym))
 512                         continue;
 513
 514                 param_name = get_param_name(tmp);
 515                 if (!param_name)
 516                         return;
 517
 518                 if (slist_has_state(tmp->possible, &user_data_set))
 519                         passed_or_new = "1";
 520                 if (slist_has_state(tmp->possible, &user_data_passed))
 521                         passed_or_new = "2";
 522
 523                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 524                                 param, param_name, passed_or_new);
 525         } END_FOR_EACH_PTR(tmp);
 526
 527         free_slist(&my_slist);
 528 }
 529
 530 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 531 {
 532         char *name;
 533         struct symbol *sym;
 534
 535         name = return_state_to_var_sym(expr, param, key, &sym);
 536         if (!name || !sym)
 537                 goto free;
 538
 539         set_state(my_id, name, sym, &user_data_set);
 540 free:
 541         free_string(name);
 542 }
 543
 544 void check_user_data(int id)
 545 {
 546         if (option_project != PROJ_KERNEL)
 547                 return;
 548         my_id = id;
 549         select_caller_info_hook(set_param_user_data, USER_DATA);
 550         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 551         add_hook(&match_condition, CONDITION_HOOK);
 552         add_hook(&match_assign, ASSIGNMENT_HOOK);
 553         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 554         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 555         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 556         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 557
 558         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 559         add_member_info_callback(my_id, struct_member_callback);
 560         add_returned_member_callback(my_id, returned_member_callback);
 561         add_returned_state_callback(print_returned_user_data);
 562         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 563
 564         add_modification_hook(my_id, &set_capped);
 565
 566         add_macro_assign_hook("ntohl", &match_macro_assign, NULL);
 567         add_macro_assign_hook("ntohs", &match_macro_assign, NULL);
 568 }