check_user_data2.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 static int my_call_id;
  31
  32 STATE(called);
  33
  34 static const char * kstr_funcs[] = {
  35         "kstrtoull", "kstrtoll", "kstrtoul", "kstrtol", "kstrtouint",
  36         "kstrtoint", "kstrtou64", "kstrtos64", "kstrtou32", "kstrtos32",
  37         "kstrtou16", "kstrtos16", "kstrtou8", "kstrtos8", "kstrtoull_from_user"
  38         "kstrtoll_from_user", "kstrtoul_from_user", "kstrtol_from_user",
  39         "kstrtouint_from_user", "kstrtoint_from_user", "kstrtou16_from_user",
  40         "kstrtos16_from_user", "kstrtou8_from_user", "kstrtos8_from_user",
  41         "kstrtou64_from_user", "kstrtos64_from_user", "kstrtou32_from_user",
  42         "kstrtos32_from_user",
  43 };
  44
  45 static void set_points_to_user_data(struct expression *expr);
  46
  47 static struct stree *start_states;
  48 static struct stree_stack *saved_stack;
  49 static void save_start_states(struct statement *stmt)
  50 {
  51         start_states = clone_stree(__get_cur_stree());
  52 }
  53
  54 static void free_start_states(void)
  55 {
  56         free_stree(&start_states);
  57 }
  58
  59 static void match_save_states(struct expression *expr)
  60 {
  61         push_stree(&saved_stack, start_states);
  62         start_states = NULL;
  63 }
  64
  65 static void match_restore_states(struct expression *expr)
  66 {
  67         free_stree(&start_states);
  68         start_states = pop_stree(&saved_stack);
  69 }
  70
  71 static struct smatch_state *empty_state(struct sm_state *sm)
  72 {
  73         return alloc_estate_empty();
  74 }
  75
  76 static void pre_merge_hook(struct sm_state *sm)
  77 {
  78         struct smatch_state *user;
  79         struct smatch_state *extra;
  80         struct range_list *rl;
  81
  82         extra = get_state(SMATCH_EXTRA, sm->name, sm->sym);
  83         if (!extra || !estate_rl(extra))
  84                 return;
  85         user = get_state(my_id, sm->name, sm->sym);
  86         if (!user || !estate_rl(user))
  87                 return;
  88         rl = rl_intersection(estate_rl(user), estate_rl(extra));
  89         set_state(my_id, sm->name, sm->sym, alloc_estate_rl(clone_rl(rl)));
  90 }
  91
  92 static void tag_inner_struct_members(struct expression *expr, struct symbol *member)
  93 {
  94         struct expression *edge_member;
  95         struct symbol *base = get_real_base_type(member);
  96         struct symbol *tmp;
  97
  98         if (member->ident)
  99                 expr = member_expression(expr, '.', member->ident);
 100
 101         FOR_EACH_PTR(base->symbol_list, tmp) {
 102                 struct symbol *type;
 103
 104                 type = get_real_base_type(tmp);
 105                 if (!type)
 106                         continue;
 107
 108                 if (type->type == SYM_UNION || type->type == SYM_STRUCT) {
 109                         tag_inner_struct_members(expr, tmp);
 110                         continue;
 111                 }
 112
 113                 if (!tmp->ident)
 114                         continue;
 115
 116                 edge_member = member_expression(expr, '.', tmp->ident);
 117                 set_state_expr(my_id, edge_member, alloc_estate_whole(type));
 118         } END_FOR_EACH_PTR(tmp);
 119 }
 120
 121 static void tag_struct_members(struct symbol *type, struct expression *expr)
 122 {
 123         struct symbol *tmp;
 124         struct expression *member;
 125         int op = '*';
 126
 127         if (expr->type == EXPR_PREOP && expr->op == '&') {
 128                 expr = strip_expr(expr->unop);
 129                 op = '.';
 130         }
 131
 132         FOR_EACH_PTR(type->symbol_list, tmp) {
 133                 type = get_real_base_type(tmp);
 134                 if (!type)
 135                         continue;
 136
 137                 if (type->type == SYM_UNION || type->type == SYM_STRUCT) {
 138                         tag_inner_struct_members(expr, tmp);
 139                         continue;
 140                 }
 141
 142                 if (!tmp->ident)
 143                         continue;
 144
 145                 member = member_expression(expr, op, tmp->ident);
 146                 set_state_expr(my_id, member, alloc_estate_whole(get_type(member)));
 147
 148                 if (type->type == SYM_ARRAY)
 149                         set_points_to_user_data(member);
 150         } END_FOR_EACH_PTR(tmp);
 151 }
 152
 153 static void tag_base_type(struct expression *expr)
 154 {
 155         if (expr->type == EXPR_PREOP && expr->op == '&')
 156                 expr = strip_expr(expr->unop);
 157         else
 158                 expr = deref_expression(expr);
 159         set_state_expr(my_id, expr, alloc_estate_whole(get_type(expr)));
 160 }
 161
 162 static void tag_as_user_data(struct expression *expr)
 163 {
 164         struct symbol *type;
 165
 166         expr = strip_expr(expr);
 167
 168         type = get_type(expr);
 169         if (!type || type->type != SYM_PTR)
 170                 return;
 171         type = get_real_base_type(type);
 172         if (!type)
 173                 return;
 174         if (type == &void_ctype) {
 175                 set_state_expr(my_id, deref_expression(expr), alloc_estate_whole(&ulong_ctype));
 176                 return;
 177         }
 178         if (type->type == SYM_BASETYPE)
 179                 tag_base_type(expr);
 180         if (type->type == SYM_STRUCT) {
 181                 if (expr->type != EXPR_PREOP || expr->op != '&')
 182                         expr = deref_expression(expr);
 183                 else
 184                         set_state_expr(my_id, deref_expression(expr), alloc_estate_whole(&ulong_ctype));
 185                 tag_struct_members(type, expr);
 186         }
 187 }
 188
 189 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 190 {
 191         int param = PTR_INT(_param);
 192         struct expression *dest;
 193
 194         dest = get_argument_from_call_expr(expr->args, param);
 195         dest = strip_expr(dest);
 196         if (!dest)
 197                 return;
 198         tag_as_user_data(dest);
 199 }
 200
 201 static void match_sscanf(const char *fn, struct expression *expr, void *unused)
 202 {
 203         struct expression *arg;
 204         int i;
 205
 206         i = -1;
 207         FOR_EACH_PTR(expr->args, arg) {
 208                 i++;
 209                 if (i < 2)
 210                         continue;
 211                 tag_as_user_data(arg);
 212         } END_FOR_EACH_PTR(arg);
 213 }
 214
 215 static int points_to_user_data(struct expression *expr)
 216 {
 217         struct smatch_state *state;
 218         char buf[256];
 219         struct symbol *sym;
 220         char *name;
 221         int ret = 0;
 222
 223         expr = strip_expr(expr);
 224
 225         if (expr->type == EXPR_BINOP && expr->op == '+') {
 226                 if (points_to_user_data(expr->left))
 227                         return 1;
 228                 if (points_to_user_data(expr->right))
 229                         return 1;
 230                 return 0;
 231         }
 232
 233         name = expr_to_var_sym(expr, &sym);
 234         if (!name || !sym)
 235                 goto free;
 236         snprintf(buf, sizeof(buf), "*%s", name);
 237         state = get_state(my_id, buf, sym);
 238         if (state && estate_rl(state))
 239                 ret = 1;
 240 free:
 241         free_string(name);
 242         return ret;
 243 }
 244
 245 static void set_points_to_user_data(struct expression *expr)
 246 {
 247         char *name;
 248         struct symbol *sym;
 249         char buf[256];
 250
 251         name = expr_to_var_sym(expr, &sym);
 252         if (!name || !sym)
 253                 goto free;
 254         snprintf(buf, sizeof(buf), "*%s", name);
 255         set_state(my_id, buf, sym, alloc_estate_whole(&llong_ctype));
 256 free:
 257         free_string(name);
 258 }
 259
 260 static int is_skb_data(struct expression *expr)
 261 {
 262         struct symbol *sym;
 263
 264         expr = strip_expr(expr);
 265         if (!expr || expr->type != EXPR_DEREF)
 266                 return 0;
 267
 268         if (!expr->member)
 269                 return 0;
 270         if (strcmp(expr->member->name, "data") != 0)
 271                 return 0;
 272
 273         sym = expr_to_sym(expr->deref);
 274         if (!sym)
 275                 return 0;
 276         sym = get_real_base_type(sym);
 277         if (!sym || sym->type != SYM_PTR)
 278                 return 0;
 279         sym = get_real_base_type(sym);
 280         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 281                 return 0;
 282         if (strcmp(sym->ident->name, "sk_buff") != 0)
 283                 return 0;
 284
 285         return 1;
 286 }
 287
 288 static int comes_from_skb_data(struct expression *expr)
 289 {
 290         expr = strip_expr(expr);
 291         if (!expr)
 292                 return 0;
 293
 294         switch (expr->type) {
 295         case EXPR_BINOP:
 296                 if (comes_from_skb_data(expr->left))
 297                         return 1;
 298                 if (comes_from_skb_data(expr->right))
 299                         return 1;
 300                 return 0;
 301         case EXPR_PREOP:
 302                 return comes_from_skb_data(expr->unop);
 303         case EXPR_DEREF:
 304                 if (is_skb_data(expr))
 305                         return 1;
 306                 return comes_from_skb_data(expr->deref);
 307         default:
 308                 return 0;
 309         }
 310 }
 311
 312
 313 static int handle_struct_assignment(struct expression *expr)
 314 {
 315         struct expression *right;
 316         struct symbol *left_type, *right_type;
 317
 318         left_type = get_type(expr->left);
 319         if (!left_type || left_type->type != SYM_PTR)
 320                 return 0;
 321         left_type = get_real_base_type(left_type);
 322         if (!left_type || left_type->type != SYM_STRUCT)
 323                 return 0;
 324
 325         /*
 326          * Ignore struct to struct assignments because for those we look at the
 327          * individual members.
 328          */
 329         right = strip_expr(expr->right);
 330         right_type = get_type(right);
 331         if (!right_type || right_type->type != SYM_PTR)
 332                 return 0;
 333
 334         /* If we are assigning struct members then normally that is handled
 335          * by fake assignments, however if we cast one struct to a different
 336          * of struct then we handle that here.
 337          */
 338         right_type = get_real_base_type(right_type);
 339         if (right_type == left_type)
 340                 return 0;
 341
 342         if (!points_to_user_data(right) && !is_skb_data(right))
 343                 return 0;
 344
 345         tag_as_user_data(expr->left);
 346         return 1;
 347 }
 348
 349 static int handle_get_user(struct expression *expr)
 350 {
 351         char *name;
 352         int ret = 0;
 353
 354         name = get_macro_name(expr->pos);
 355         if (!name || strcmp(name, "get_user") != 0)
 356                 return 0;
 357
 358         name = expr_to_var(expr->right);
 359         if (!name || strcmp(name, "__val_gu") != 0)
 360                 goto free;
 361         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 362         ret = 1;
 363 free:
 364         free_string(name);
 365         return ret;
 366 }
 367
 368 static void match_assign(struct expression *expr)
 369 {
 370         struct range_list *rl;
 371
 372         if (is_fake_call(expr->right))
 373                 return;
 374         if (handle_get_user(expr))
 375                 return;
 376         if (points_to_user_data(expr->right))
 377                 set_points_to_user_data(expr->left);
 378         if (handle_struct_assignment(expr))
 379                 return;
 380
 381         if (expr->right->type == EXPR_CALL ||
 382             !get_user_rl(expr->right, &rl))
 383                 goto clear_old_state;
 384
 385         rl = cast_rl(get_type(expr->left), rl);
 386         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 387
 388         return;
 389
 390 clear_old_state:
 391         if (get_state_expr(my_id, expr->left))
 392                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 393 }
 394
 395 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 396 {
 397         tag_as_user_data(expr->left);
 398         set_points_to_user_data(expr->left);
 399 }
 400
 401 static void match_simple_strtoul(const char *fn, struct expression *expr, void *unused)
 402 {
 403         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 404 }
 405
 406 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 407 {
 408         char *macro;
 409
 410         if (!expr)
 411                 return 0;
 412         macro = get_macro_name(expr->pos);
 413
 414         if (!macro)
 415                 return 0;
 416
 417         if (strcmp(macro, "ntohl") == 0) {
 418                 *rl = alloc_whole_rl(&uint_ctype);
 419                 return 1;
 420         }
 421         if (strcmp(macro, "ntohs") == 0) {
 422                 *rl = alloc_whole_rl(&ushort_ctype);
 423                 return 1;
 424         }
 425         return 0;
 426 }
 427
 428 static int user_data_flag;
 429 static struct range_list *var_user_rl(struct expression *expr)
 430 {
 431         struct smatch_state *state;
 432         struct range_list *rl;
 433         struct range_list *absolute_rl;
 434
 435         if (get_user_macro_rl(expr, &rl))
 436                 goto found;
 437
 438         if (comes_from_skb_data(expr)) {
 439                 rl = alloc_whole_rl(get_type(expr));
 440                 goto found;
 441         }
 442
 443         state = get_state_expr(my_id, expr);
 444         if (state && estate_rl(state)) {
 445                 rl = estate_rl(state);
 446                 goto found;
 447         }
 448
 449         return NULL;
 450 found:
 451         user_data_flag = 1;
 452         absolute_rl = var_to_absolute_rl(expr);
 453         return clone_rl(rl_intersection(rl, absolute_rl));
 454 }
 455
 456 int get_user_rl(struct expression *expr, struct range_list **rl)
 457 {
 458
 459         user_data_flag = 0;
 460         custom_get_absolute_rl(expr, &var_user_rl, rl);
 461         if (!user_data_flag) {
 462                 *rl = NULL;
 463                 return 0;
 464         }
 465         return 1;
 466 }
 467
 468 int get_user_rl_var_sym(const char *name, struct symbol *sym, struct range_list **rl)
 469 {
 470         struct smatch_state *state;
 471
 472         state = get_state(my_id, name, sym);
 473         if (state && estate_rl(state)) {
 474                 *rl = estate_rl(state);
 475                 return 1;
 476         }
 477         return 0;
 478 }
 479
 480 static void match_call_info(struct expression *expr)
 481 {
 482         struct range_list *rl;
 483         struct expression *arg;
 484         int i = 0;
 485
 486         i = -1;
 487         FOR_EACH_PTR(expr->args, arg) {
 488                 i++;
 489
 490                 if (!get_user_rl(arg, &rl))
 491                         continue;
 492
 493                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 494         } END_FOR_EACH_PTR(arg);
 495 }
 496
 497 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 498 {
 499         struct smatch_state *state;
 500         struct range_list *rl;
 501
 502         if (strcmp(sm->state->name, "") == 0)
 503                 return;
 504
 505         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 506         if (!state || !estate_rl(state))
 507                 rl = estate_rl(sm->state);
 508         else
 509                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 510
 511         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 512 }
 513
 514 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 515 {
 516         struct range_list *rl = NULL;
 517         struct smatch_state *state;
 518         struct symbol *type;
 519         char fullname[256];
 520
 521         if (strcmp(key, "*$") == 0)
 522                 snprintf(fullname, sizeof(fullname), "*%s", name);
 523         else if (strncmp(key, "$", 1) == 0)
 524                 snprintf(fullname, 256, "%s%s", name, key + 1);
 525         else
 526                 return;
 527
 528         type = get_member_type_from_key(symbol_expression(sym), key);
 529
 530         /* if the caller passes a void pointer with user data */
 531         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 532                 struct expression *expr = symbol_expression(sym);
 533
 534                 tag_as_user_data(expr);
 535                 set_points_to_user_data(expr);
 536                 return;
 537         }
 538         str_to_rl(type, value, &rl);
 539         state = alloc_estate_rl(rl);
 540         set_state(my_id, fullname, sym, state);
 541 }
 542
 543 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 544 {
 545         set_state(my_call_id, "this_function", NULL, &called);
 546 }
 547
 548 static void match_syscall_definition(struct symbol *sym)
 549 {
 550         struct symbol *arg;
 551         char *macro;
 552         char *name;
 553         int is_syscall = 0;
 554
 555         macro = get_macro_name(sym->pos);
 556         if (macro &&
 557             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 558              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 559                 is_syscall = 1;
 560
 561         name = get_function();
 562         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 563                 if (name && strncmp(name, "sys_", 4) == 0)
 564                         is_syscall = 1;
 565         }
 566
 567         if (name && strncmp(name, "compat_sys_", 11) == 0)
 568                 is_syscall = 1;
 569
 570         if (!is_syscall)
 571                 return;
 572
 573         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 574                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 575         } END_FOR_EACH_PTR(arg);
 576 }
 577
 578 static void returns_param_user_data(struct expression *expr, int param, char *key, char *value)
 579 {
 580         struct expression *arg;
 581         char *name;
 582         struct symbol *sym;
 583         struct symbol *type;
 584         struct range_list *rl = NULL;
 585
 586         while (expr->type == EXPR_ASSIGNMENT)
 587                 expr = strip_expr(expr->right);
 588         if (expr->type != EXPR_CALL)
 589                 return;
 590
 591         arg = get_argument_from_call_expr(expr->args, param);
 592         if (!arg)
 593                 return;
 594         type = get_member_type_from_key(arg, key);
 595         name = get_variable_from_key(arg, key, &sym);
 596         if (!name || !sym)
 597                 goto free;
 598
 599         call_results_to_rl(expr, type, value, &rl);
 600
 601         set_state(my_id, name, sym, alloc_estate_rl(rl));
 602 free:
 603         free_string(name);
 604 }
 605
 606 static int has_empty_state(struct sm_state *sm)
 607 {
 608         struct sm_state *tmp;
 609
 610         FOR_EACH_PTR(sm->possible, tmp) {
 611                 if (!estate_rl(tmp->state))
 612                         return 1;
 613         } END_FOR_EACH_PTR(tmp);
 614
 615         return 0;
 616 }
 617
 618 static void param_set_to_user_data(int return_id, char *return_ranges, struct expression *expr)
 619 {
 620         struct sm_state *sm;
 621         struct smatch_state *start_state;
 622         int param;
 623         const char *param_name;
 624
 625         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 626                 if (has_empty_state(sm))
 627                         continue;
 628
 629                 param = get_param_num_from_sym(sm->sym);
 630                 if (param < 0) {
 631                         if (expr_to_sym(expr) == sm->sym)
 632                                 param = -1;
 633                         else
 634                                 continue;
 635                 }
 636
 637                 /* The logic here was that if we were passed in a user data then
 638                  * we don't record that.  It's like the difference between
 639                  * param_filter and param_set.  When I think about it, I'm not
 640                  * sure it actually works.  It's probably harmless because we
 641                  * checked earlier that we're not returning a parameter...
 642                  * Let's mark this as a TODO.
 643                  */
 644                 start_state = get_state_stree(start_states, my_id, sm->name, sm->sym);
 645                 if (start_state && estates_equiv(sm->state, start_state))
 646                         continue;
 647
 648                 param_name = get_param_name(sm);
 649                 if (!param_name)
 650                         continue;
 651                 if (strcmp(param_name, "$") == 0)
 652                         continue;
 653
 654                 sql_insert_return_states(return_id, return_ranges, USER_DATA3,
 655                                          param, param_name, show_rl(estate_rl(sm->state)));
 656         } END_FOR_EACH_SM(sm);
 657 }
 658
 659 void check_user_data2(int id)
 660 {
 661         int i;
 662
 663         my_id = id;
 664
 665         if (option_project != PROJ_KERNEL)
 666                 return;
 667
 668         add_hook(&save_start_states, AFTER_DEF_HOOK);
 669         add_hook(&free_start_states, AFTER_FUNC_HOOK);
 670         add_hook(&match_save_states, INLINE_FN_START);
 671         add_hook(&match_restore_states, INLINE_FN_END);
 672
 673         add_unmatched_state_hook(my_id, &empty_state);
 674         add_pre_merge_hook(my_id, &pre_merge_hook);
 675         add_merge_hook(my_id, &merge_estates);
 676
 677         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 678         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 679         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 680         for (i = 0; i < ARRAY_SIZE(kstr_funcs); i++)
 681                 add_function_hook(kstr_funcs[i], &match_user_copy, INT_PTR(2));
 682
 683         add_function_assign_hook("simple_strtol", &match_simple_strtoul, NULL);
 684         add_function_assign_hook("simple_strtoll", &match_simple_strtoul, NULL);
 685         add_function_assign_hook("simple_strtoul", &match_simple_strtoul, NULL);
 686         add_function_assign_hook("simple_strtoull", &match_simple_strtoul, NULL);
 687
 688         add_function_hook("sscanf", &match_sscanf, NULL);
 689
 690         add_function_assign_hook("memdup_user", &match_user_assign_function, NULL);
 691         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 692         add_function_assign_hook("skb_network_header", &match_user_assign_function, NULL);
 693
 694         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 695
 696         add_hook(&match_assign, ASSIGNMENT_HOOK);
 697
 698         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 699         add_member_info_callback(my_id, struct_member_callback);
 700         select_caller_info_hook(set_param_user_data, USER_DATA3);
 701         select_return_states_hook(USER_DATA3, &returns_param_user_data);
 702         add_split_return_callback(&param_set_to_user_data);
 703 }
 704
 705 void check_user_data3(int id)
 706 {
 707         my_call_id = id;
 708
 709         if (option_project != PROJ_KERNEL)
 710                 return;
 711         select_caller_info_hook(set_called, INTERNAL);
 712 }
 713