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 (expr->fn->type != EXPR_SYMBOL)
 104                 return 0;
 105         sym = expr->fn->symbol;
 106         if (!sym)
 107                 return 0;
 108
 109         if (sym->ctype.modifiers & MOD_STATIC) {
 110                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 111                          get_filename(), sym->ident->name);
 112         } else {
 113                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 114                                 sym->ident->name);
 115         }
 116
 117         db_expr = expr;
 118         db_user_data = 0;
 119         run_sql(db_user_data_callback,
 120                 "select value from return_states where type=%d and parameter = -1 and key = '$$' and %s",
 121                 USER_DATA, sql_filter);
 122         return db_user_data;
 123 }
 124
 125 static int is_user_function(struct expression *expr)
 126 {
 127         if (expr->type != EXPR_CALL)
 128                 return 0;
 129         return is_user_fn_db(expr);
 130 }
 131
 132 static int is_skb_data(struct expression *expr)
 133 {
 134         struct symbol *sym;
 135         char *name;
 136         int len;
 137         int ret = 0;
 138
 139         name = expr_to_var_sym(expr, &sym);
 140         if (!name || !sym)
 141                 goto free;
 142
 143         sym = get_base_type(sym);
 144         if (!sym || sym->type != SYM_PTR)
 145                 goto free;
 146         sym = get_base_type(sym);
 147         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 148                 goto free;
 149         if (strcmp(sym->ident->name, "sk_buff") != 0)
 150                 goto free;
 151
 152         len = strlen(name);
 153         if (len < 6)
 154                 goto free;
 155         if (strcmp(name + len - 6, "->data") == 0)
 156                 ret = SET_DATA;
 157
 158 free:
 159         free_string(name);
 160         return ret;
 161 }
 162
 163 static int in_container_of_macro(struct expression *expr)
 164 {
 165         char *macro;
 166
 167         macro = get_macro_name(expr->pos);
 168
 169         if (!macro)
 170                 return 0;
 171         if (strcmp(macro, "container_of") == 0)
 172                 return 1;
 173         return 0;
 174 }
 175
 176 static int is_user_data_state(struct expression *expr)
 177 {
 178         struct state_list *slist = NULL;
 179         struct sm_state *tmp;
 180         struct symbol *sym;
 181         char *name;
 182         int user = 0;
 183
 184         tmp = get_sm_state_expr(my_id, expr);
 185         if (tmp) {
 186                 if (slist_has_state(tmp->possible, &user_data_set))
 187                         return SET_DATA;
 188                 if (slist_has_state(tmp->possible, &user_data_passed))
 189                         return PASSED_DATA;
 190                 return 0;
 191         }
 192
 193         name = expr_to_str_sym(expr, &sym);
 194         if (!name || !sym)
 195                 goto free;
 196
 197         slist = get_all_states(my_id);
 198         FOR_EACH_PTR(slist, tmp) {
 199                 if (tmp->sym != sym)
 200                         continue;
 201                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 202                         if (slist_has_state(tmp->possible, &user_data_set))
 203                                 user = SET_DATA;
 204                         else if (slist_has_state(tmp->possible, &user_data_passed))
 205                                 user = PASSED_DATA;
 206                         goto free;
 207                 }
 208         } END_FOR_EACH_PTR(tmp);
 209
 210 free:
 211         free_slist(&slist);
 212         free_string(name);
 213         return user;
 214 }
 215
 216 int is_user_data(struct expression *expr)
 217 {
 218         int user_data;
 219
 220         if (!expr)
 221                 return 0;
 222
 223         if (is_capped(expr))
 224                 return 0;
 225         if (in_container_of_macro(expr))
 226                 return 0;
 227
 228         user_data = is_user_macro(expr);
 229         if (user_data)
 230                 return user_data;
 231         user_data = is_user_function(expr);
 232         if (user_data)
 233                 return user_data;
 234         user_data = is_skb_data(expr);
 235         if (user_data)
 236                 return user_data;
 237
 238         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 239
 240         if (expr->type == EXPR_BINOP) {
 241                 user_data = is_user_data(expr->left);
 242                 if (user_data)
 243                         return user_data;
 244                 if (is_array(expr))
 245                         return 0;
 246                 user_data = is_user_data(expr->right);
 247                 if (user_data)
 248                         return user_data;
 249                 return 0;
 250         }
 251         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 252                 expr = strip_expr(expr->unop);
 253
 254         return is_user_data_state(expr);
 255 }
 256
 257 int is_capped_user_data(struct expression *expr)
 258 {
 259         struct sm_state *sm;
 260
 261         sm = get_sm_state_expr(my_id, expr);
 262         if (!sm)
 263                 return 0;
 264         if (slist_has_state(sm->possible, &capped))
 265                 return 1;
 266         return 0;
 267 }
 268
 269 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 270 {
 271         char fullname[256];
 272
 273         /* sanity check.  this should always be true. */
 274         if (strncmp(key, "$$", 2) != 0)
 275                 return;
 276         snprintf(fullname, 256, "%s%s", name, key + 2);
 277         set_state(my_id, fullname, sym, &user_data_passed);
 278 }
 279
 280 static void match_syscall_definition(struct symbol *sym)
 281 {
 282         struct symbol *arg;
 283         char *macro;
 284
 285         macro = get_macro_name(sym->pos);
 286         if (!macro)
 287                 return;
 288         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 289             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 290                 return;
 291
 292         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 293                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 294         } END_FOR_EACH_PTR(arg);
 295 }
 296
 297 static void match_condition(struct expression *expr)
 298 {
 299         switch (expr->op) {
 300         case '<':
 301         case SPECIAL_LTE:
 302         case SPECIAL_UNSIGNED_LT:
 303         case SPECIAL_UNSIGNED_LTE:
 304                 if (is_user_data(expr->left))
 305                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 306                 if (is_user_data(expr->right))
 307                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 308                 break;
 309         case '>':
 310         case SPECIAL_GTE:
 311         case SPECIAL_UNSIGNED_GT:
 312         case SPECIAL_UNSIGNED_GTE:
 313                 if (is_user_data(expr->right))
 314                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 315                 if (is_user_data(expr->left))
 316                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 317                 break;
 318         case SPECIAL_EQUAL:
 319                 if (is_user_data(expr->left))
 320                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 321                 if (is_user_data(expr->right))
 322                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 323                 break;
 324         case SPECIAL_NOTEQUAL:
 325                 if (is_user_data(expr->left))
 326                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 327                 if (is_user_data(expr->right))
 328                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 329                 break;
 330         default:
 331                 return;
 332         }
 333 }
 334
 335 static void set_capped(struct sm_state *sm, struct expression *mod_expr)
 336 {
 337         set_state(my_id, sm->name, sm->sym, &capped);
 338 }
 339
 340 static void match_normal_assign(struct expression *expr)
 341 {
 342         int user_data;
 343
 344         user_data = is_user_data(expr->right);
 345         if (user_data == PASSED_DATA)
 346                 set_state_expr(my_id, expr->left, &user_data_passed);
 347         if (user_data == SET_DATA)
 348                 set_state_expr(my_id, expr->left, &user_data_set);
 349 }
 350
 351 static void match_assign(struct expression *expr)
 352 {
 353         char *name;
 354
 355         name = get_macro_name(expr->pos);
 356         if (!name || strcmp(name, "get_user") != 0) {
 357                 match_normal_assign(expr);
 358                 return;
 359         }
 360         name = expr_to_var(expr->right);
 361         if (!name || strcmp(name, "__val_gu") != 0)
 362                 goto free;
 363         set_state_expr(my_id, expr->left, &user_data_set);
 364 free:
 365         free_string(name);
 366 }
 367
 368 static void tag_struct_members(struct symbol *type, struct expression *expr)
 369 {
 370         struct symbol *tmp;
 371         struct expression *member;
 372         int op = '*';
 373
 374         if (expr->type == EXPR_PREOP && expr->op == '&') {
 375                 expr = strip_expr(expr->unop);
 376                 op = '.';
 377         }
 378
 379         FOR_EACH_PTR(type->symbol_list, tmp) {
 380                 if (!tmp->ident)
 381                         continue;
 382                 member = member_expression(expr, op, tmp->ident);
 383                 set_state_expr(my_id, member, &user_data_set);
 384         } END_FOR_EACH_PTR(tmp);
 385 }
 386
 387 static void tag_base_type(struct expression *expr)
 388 {
 389         if (expr->type == EXPR_PREOP && expr->op == '&')
 390                 expr = strip_expr(expr->unop);
 391         else
 392                 expr = deref_expression(expr);
 393         set_state_expr(my_id, expr, &user_data_set);
 394 }
 395
 396 static void tag_as_user_data(struct expression *expr)
 397 {
 398         struct symbol *type;
 399
 400         expr = strip_expr(expr);
 401
 402         type = get_type(expr);
 403         if (!type || type->type != SYM_PTR)
 404                 return;
 405         type = get_real_base_type(type);
 406         if (!type)
 407                 return;
 408         if (type == &void_ctype) {
 409                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 410                 return;
 411         }
 412         if (type->type == SYM_BASETYPE)
 413                 tag_base_type(expr);
 414         if (type->type == SYM_STRUCT) {
 415                 if (expr->type != EXPR_PREOP || expr->op != '&')
 416                         expr = deref_expression(expr);
 417                 tag_struct_members(type, expr);
 418         }
 419 }
 420
 421 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 422 {
 423         int param = PTR_INT(_param);
 424         struct expression *dest;
 425
 426         dest = get_argument_from_call_expr(expr->args, param);
 427         dest = strip_expr(dest);
 428         if (!dest)
 429                 return;
 430         tag_as_user_data(dest);
 431 }
 432
 433 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 434 {
 435         set_state_expr(my_id, expr->left, &user_data_set);
 436 }
 437
 438 static void match_macro_assign(const char *fn, struct expression *expr, void *_bits)
 439 {
 440         int bits;
 441
 442         bits = nr_bits(expr->left);
 443         if (!bits)
 444                 return;
 445         if (bits > nr_bits(expr->right))
 446                 return;
 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, "$$", "1");
 493         }
 494
 495         my_slist = get_all_states(my_id);
 496
 497         FOR_EACH_PTR(my_slist, tmp) {
 498                 const char *param_name;
 499
 500                 param = get_param_num_from_sym(tmp->sym);
 501                 if (param < 0)
 502                         continue;
 503
 504                 if (is_capped_var_sym(tmp->name, tmp->sym))
 505                         continue;
 506                 /* ignore states that were already USER_DATA to begin with */
 507                 if (get_state_slist(get_start_states(), my_id, tmp->name, tmp->sym))
 508                         continue;
 509
 510                 param_name = get_param_name(tmp);
 511                 if (!param_name)
 512                         return;
 513
 514                 if (slist_has_state(tmp->possible, &user_data_set))
 515                         passed_or_new = "1";
 516                 else if (slist_has_state(tmp->possible, &user_data_passed))
 517                         passed_or_new = "2";
 518                 else
 519                         continue;
 520
 521                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 522                                 param, param_name, passed_or_new);
 523         } END_FOR_EACH_PTR(tmp);
 524
 525         free_slist(&my_slist);
 526 }
 527
 528 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 529 {
 530         char *name;
 531         struct symbol *sym;
 532
 533         if (expr->type == EXPR_ASSIGNMENT && param == -1 && strcmp(key, "*$$") == 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
 567         add_modification_hook(my_id, &set_capped);
 568
 569         add_macro_assign_hook("ntohl", &match_macro_assign, NULL);
 570         add_macro_assign_hook("ntohs", &match_macro_assign, NULL);
 571 }