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 }
 122
 123 static void tag_struct_members(struct symbol *type, struct expression *expr)
 124 {
 125         struct symbol *tmp;
 126         struct expression *member;
 127         int op = '*';
 128
 129         if (expr->type == EXPR_PREOP && expr->op == '&') {
 130                 expr = strip_expr(expr->unop);
 131                 op = '.';
 132         }
 133
 134         FOR_EACH_PTR(type->symbol_list, tmp) {
 135                 type = get_real_base_type(tmp);
 136                 if (!type)
 137                         continue;
 138
 139                 if (type->type == SYM_UNION || type->type == SYM_STRUCT) {
 140                         tag_inner_struct_members(expr, tmp);
 141                         continue;
 142                 }
 143
 144                 if (!tmp->ident)
 145                         continue;
 146
 147                 member = member_expression(expr, op, tmp->ident);
 148                 set_state_expr(my_id, member, alloc_estate_whole(get_type(member)));
 149
 150                 if (type->type == SYM_ARRAY)
 151                         set_points_to_user_data(member);
 152         } END_FOR_EACH_PTR(tmp);
 153 }
 154
 155 static void tag_base_type(struct expression *expr)
 156 {
 157         if (expr->type == EXPR_PREOP && expr->op == '&')
 158                 expr = strip_expr(expr->unop);
 159         else
 160                 expr = deref_expression(expr);
 161         set_state_expr(my_id, expr, alloc_estate_whole(get_type(expr)));
 162 }
 163
 164 static void tag_as_user_data(struct expression *expr)
 165 {
 166         struct symbol *type;
 167
 168         expr = strip_expr(expr);
 169
 170         type = get_type(expr);
 171         if (!type || type->type != SYM_PTR)
 172                 return;
 173         type = get_real_base_type(type);
 174         if (!type)
 175                 return;
 176         if (type == &void_ctype) {
 177                 set_state_expr(my_id, deref_expression(expr), alloc_estate_whole(&ulong_ctype));
 178                 return;
 179         }
 180         if (type->type == SYM_BASETYPE)
 181                 tag_base_type(expr);
 182         if (type->type == SYM_STRUCT) {
 183                 if (expr->type != EXPR_PREOP || expr->op != '&')
 184                         expr = deref_expression(expr);
 185                 else
 186                         set_state_expr(my_id, deref_expression(expr), alloc_estate_whole(&ulong_ctype));
 187                 tag_struct_members(type, expr);
 188         }
 189 }
 190
 191 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 192 {
 193         int param = PTR_INT(_param);
 194         struct expression *dest;
 195
 196         dest = get_argument_from_call_expr(expr->args, param);
 197         dest = strip_expr(dest);
 198         if (!dest)
 199                 return;
 200         tag_as_user_data(dest);
 201 }
 202
 203 static void match_sscanf(const char *fn, struct expression *expr, void *unused)
 204 {
 205         struct expression *arg;
 206         int i;
 207
 208         i = -1;
 209         FOR_EACH_PTR(expr->args, arg) {
 210                 i++;
 211                 if (i < 2)
 212                         continue;
 213                 tag_as_user_data(arg);
 214         } END_FOR_EACH_PTR(arg);
 215 }
 216
 217 static int points_to_user_data(struct expression *expr)
 218 {
 219         struct smatch_state *state;
 220         char buf[256];
 221         struct symbol *sym;
 222         char *name;
 223         int ret = 0;
 224
 225         expr = strip_expr(expr);
 226
 227         if (expr->type == EXPR_BINOP && expr->op == '+') {
 228                 if (points_to_user_data(expr->left))
 229                         return 1;
 230                 if (points_to_user_data(expr->right))
 231                         return 1;
 232                 return 0;
 233         }
 234
 235         name = expr_to_var_sym(expr, &sym);
 236         if (!name || !sym)
 237                 goto free;
 238         snprintf(buf, sizeof(buf), "*%s", name);
 239         state = get_state(my_id, buf, sym);
 240         if (state && estate_rl(state))
 241                 ret = 1;
 242 free:
 243         free_string(name);
 244         return ret;
 245 }
 246
 247 static void set_points_to_user_data(struct expression *expr)
 248 {
 249         char *name;
 250         struct symbol *sym;
 251         char buf[256];
 252
 253         name = expr_to_var_sym(expr, &sym);
 254         if (!name || !sym)
 255                 goto free;
 256         snprintf(buf, sizeof(buf), "*%s", name);
 257         set_state(my_id, buf, sym, alloc_estate_whole(&llong_ctype));
 258 free:
 259         free_string(name);
 260 }
 261
 262 static int is_skb_data(struct expression *expr)
 263 {
 264         struct symbol *sym;
 265
 266         expr = strip_expr(expr);
 267         if (!expr || expr->type != EXPR_DEREF)
 268                 return 0;
 269
 270         if (!expr->member)
 271                 return 0;
 272         if (strcmp(expr->member->name, "data") != 0)
 273                 return 0;
 274
 275         sym = expr_to_sym(expr->deref);
 276         if (!sym)
 277                 return 0;
 278         sym = get_real_base_type(sym);
 279         if (!sym || sym->type != SYM_PTR)
 280                 return 0;
 281         sym = get_real_base_type(sym);
 282         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 283                 return 0;
 284         if (strcmp(sym->ident->name, "sk_buff") != 0)
 285                 return 0;
 286
 287         return 1;
 288 }
 289
 290 static int comes_from_skb_data(struct expression *expr)
 291 {
 292         expr = strip_expr(expr);
 293         if (!expr)
 294                 return 0;
 295
 296         switch (expr->type) {
 297         case EXPR_BINOP:
 298                 if (comes_from_skb_data(expr->left))
 299                         return 1;
 300                 if (comes_from_skb_data(expr->right))
 301                         return 1;
 302                 return 0;
 303         case EXPR_PREOP:
 304                 return comes_from_skb_data(expr->unop);
 305         case EXPR_DEREF:
 306                 if (is_skb_data(expr))
 307                         return 1;
 308                 return comes_from_skb_data(expr->deref);
 309         default:
 310                 return 0;
 311         }
 312 }
 313
 314
 315 static int handle_struct_assignment(struct expression *expr)
 316 {
 317         struct expression *right;
 318         struct symbol *left_type, *right_type;
 319
 320         left_type = get_type(expr->left);
 321         if (!left_type || left_type->type != SYM_PTR)
 322                 return 0;
 323         left_type = get_real_base_type(left_type);
 324         if (!left_type || left_type->type != SYM_STRUCT)
 325                 return 0;
 326
 327         /*
 328          * Ignore struct to struct assignments because for those we look at the
 329          * individual members.
 330          */
 331         right = strip_expr(expr->right);
 332         right_type = get_type(right);
 333         if (!right_type || right_type->type != SYM_PTR)
 334                 return 0;
 335
 336         /* If we are assigning struct members then normally that is handled
 337          * by fake assignments, however if we cast one struct to a different
 338          * of struct then we handle that here.
 339          */
 340         right_type = get_real_base_type(right_type);
 341         if (right_type == left_type)
 342                 return 0;
 343
 344         if (!points_to_user_data(right) && !is_skb_data(right))
 345                 return 0;
 346
 347         tag_as_user_data(expr->left);
 348         return 1;
 349 }
 350
 351 static int handle_get_user(struct expression *expr)
 352 {
 353         char *name;
 354         int ret = 0;
 355
 356         name = get_macro_name(expr->pos);
 357         if (!name || strcmp(name, "get_user") != 0)
 358                 return 0;
 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, alloc_estate_whole(get_type(expr->left)));
 364         ret = 1;
 365 free:
 366         free_string(name);
 367         return ret;
 368 }
 369
 370 static void match_assign(struct expression *expr)
 371 {
 372         struct range_list *rl;
 373
 374         if (is_fake_call(expr->right))
 375                 return;
 376         if (handle_get_user(expr))
 377                 return;
 378         if (points_to_user_data(expr->right))
 379                 set_points_to_user_data(expr->left);
 380         if (handle_struct_assignment(expr))
 381                 return;
 382
 383         if (expr->right->type == EXPR_CALL ||
 384             !get_user_rl(expr->right, &rl))
 385                 goto clear_old_state;
 386
 387         rl = cast_rl(get_type(expr->left), rl);
 388         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 389
 390         return;
 391
 392 clear_old_state:
 393         if (get_state_expr(my_id, expr->left))
 394                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 395 }
 396
 397 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 398 {
 399         tag_as_user_data(expr->left);
 400         set_points_to_user_data(expr->left);
 401 }
 402
 403 static void match_simple_strtoul(const char *fn, struct expression *expr, void *unused)
 404 {
 405         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 406 }
 407
 408 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 409 {
 410         char *macro;
 411
 412         if (!expr)
 413                 return 0;
 414         macro = get_macro_name(expr->pos);
 415
 416         if (!macro)
 417                 return 0;
 418
 419         if (strcmp(macro, "ntohl") == 0) {
 420                 *rl = alloc_whole_rl(&uint_ctype);
 421                 return 1;
 422         }
 423         if (strcmp(macro, "ntohs") == 0) {
 424                 *rl = alloc_whole_rl(&ushort_ctype);
 425                 return 1;
 426         }
 427         return 0;
 428 }
 429
 430 static int user_data_flag;
 431 static struct range_list *var_user_rl(struct expression *expr)
 432 {
 433         struct smatch_state *state;
 434         struct range_list *rl;
 435         struct range_list *absolute_rl;
 436
 437         if (get_user_macro_rl(expr, &rl))
 438                 goto found;
 439
 440         if (comes_from_skb_data(expr)) {
 441                 rl = alloc_whole_rl(get_type(expr));
 442                 goto found;
 443         }
 444
 445         state = get_state_expr(my_id, expr);
 446         if (state && estate_rl(state)) {
 447                 rl = estate_rl(state);
 448                 goto found;
 449         }
 450
 451         return NULL;
 452 found:
 453         user_data_flag = 1;
 454         absolute_rl = var_to_absolute_rl(expr);
 455         return clone_rl(rl_intersection(rl, absolute_rl));
 456 }
 457
 458 int get_user_rl(struct expression *expr, struct range_list **rl)
 459 {
 460
 461         user_data_flag = 0;
 462         custom_get_absolute_rl(expr, &var_user_rl, rl);
 463         if (!user_data_flag) {
 464                 *rl = NULL;
 465                 return 0;
 466         }
 467         return 1;
 468 }
 469
 470 int get_user_rl_var_sym(const char *name, struct symbol *sym, struct range_list **rl)
 471 {
 472         struct smatch_state *state;
 473
 474         state = get_state(my_id, name, sym);
 475         if (state && estate_rl(state)) {
 476                 *rl = estate_rl(state);
 477                 return 1;
 478         }
 479         return 0;
 480 }
 481
 482 static void match_call_info(struct expression *expr)
 483 {
 484         struct range_list *rl;
 485         struct expression *arg;
 486         int i = 0;
 487
 488         i = -1;
 489         FOR_EACH_PTR(expr->args, arg) {
 490                 i++;
 491
 492                 if (!get_user_rl(arg, &rl))
 493                         continue;
 494
 495                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 496         } END_FOR_EACH_PTR(arg);
 497 }
 498
 499 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 500 {
 501         struct smatch_state *state;
 502         struct range_list *rl;
 503
 504         if (strcmp(sm->state->name, "") == 0)
 505                 return;
 506
 507         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 508         if (!state || !estate_rl(state))
 509                 rl = estate_rl(sm->state);
 510         else
 511                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 512
 513         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 514 }
 515
 516 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 517 {
 518         struct range_list *rl = NULL;
 519         struct smatch_state *state;
 520         struct symbol *type;
 521         char fullname[256];
 522
 523         if (strcmp(key, "*$") == 0)
 524                 snprintf(fullname, sizeof(fullname), "*%s", name);
 525         else if (strncmp(key, "$", 1) == 0)
 526                 snprintf(fullname, 256, "%s%s", name, key + 1);
 527         else
 528                 return;
 529
 530         type = get_member_type_from_key(symbol_expression(sym), key);
 531
 532         /* if the caller passes a void pointer with user data */
 533         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 534                 struct expression *expr = symbol_expression(sym);
 535
 536                 tag_as_user_data(expr);
 537                 set_points_to_user_data(expr);
 538                 return;
 539         }
 540         str_to_rl(type, value, &rl);
 541         state = alloc_estate_rl(rl);
 542         set_state(my_id, fullname, sym, state);
 543 }
 544
 545 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 546 {
 547         set_state(my_call_id, "this_function", NULL, &called);
 548 }
 549
 550 static void match_syscall_definition(struct symbol *sym)
 551 {
 552         struct symbol *arg;
 553         char *macro;
 554         char *name;
 555         int is_syscall = 0;
 556
 557         macro = get_macro_name(sym->pos);
 558         if (macro &&
 559             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 560              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 561                 is_syscall = 1;
 562
 563         name = get_function();
 564         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 565                 if (name && strncmp(name, "sys_", 4) == 0)
 566                         is_syscall = 1;
 567         }
 568
 569         if (name && strncmp(name, "compat_sys_", 11) == 0)
 570                 is_syscall = 1;
 571
 572         if (!is_syscall)
 573                 return;
 574
 575         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 576                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 577         } END_FOR_EACH_PTR(arg);
 578 }
 579
 580 static void returns_param_user_data(struct expression *expr, int param, char *key, char *value)
 581 {
 582         struct expression *arg;
 583         char *name;
 584         struct symbol *sym;
 585         struct symbol *type;
 586         struct range_list *rl = NULL;
 587
 588         while (expr->type == EXPR_ASSIGNMENT)
 589                 expr = strip_expr(expr->right);
 590         if (expr->type != EXPR_CALL)
 591                 return;
 592
 593         arg = get_argument_from_call_expr(expr->args, param);
 594         if (!arg)
 595                 return;
 596         type = get_member_type_from_key(arg, key);
 597         name = get_variable_from_key(arg, key, &sym);
 598         if (!name || !sym)
 599                 goto free;
 600
 601         call_results_to_rl(expr, type, value, &rl);
 602
 603         set_state(my_id, name, sym, alloc_estate_rl(rl));
 604 free:
 605         free_string(name);
 606 }
 607
 608 static int has_empty_state(struct sm_state *sm)
 609 {
 610         struct sm_state *tmp;
 611
 612         FOR_EACH_PTR(sm->possible, tmp) {
 613                 if (!estate_rl(tmp->state))
 614                         return 1;
 615         } END_FOR_EACH_PTR(tmp);
 616
 617         return 0;
 618 }
 619
 620 static void param_set_to_user_data(int return_id, char *return_ranges, struct expression *expr)
 621 {
 622         struct sm_state *sm;
 623         struct smatch_state *start_state;
 624         int param;
 625         const char *param_name;
 626
 627         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 628                 if (has_empty_state(sm))
 629                         continue;
 630
 631                 param = get_param_num_from_sym(sm->sym);
 632                 if (param < 0) {
 633                         if (expr_to_sym(expr) == sm->sym)
 634                                 param = -1;
 635                         else
 636                                 continue;
 637                 }
 638
 639                 /* The logic here was that if we were passed in a user data then
 640                  * we don't record that.  It's like the difference between
 641                  * param_filter and param_set.  When I think about it, I'm not
 642                  * sure it actually works.  It's probably harmless because we
 643                  * checked earlier that we're not returning a parameter...
 644                  * Let's mark this as a TODO.
 645                  */
 646                 start_state = get_state_stree(start_states, my_id, sm->name, sm->sym);
 647                 if (start_state && estates_equiv(sm->state, start_state))
 648                         continue;
 649
 650                 param_name = get_param_name(sm);
 651                 if (!param_name)
 652                         continue;
 653                 if (strcmp(param_name, "$") == 0)
 654                         continue;
 655
 656                 sql_insert_return_states(return_id, return_ranges, USER_DATA3,
 657                                          param, param_name, show_rl(estate_rl(sm->state)));
 658         } END_FOR_EACH_SM(sm);
 659 }
 660
 661 void check_user_data2(int id)
 662 {
 663         int i;
 664
 665         my_id = id;
 666
 667         if (option_project != PROJ_KERNEL)
 668                 return;
 669
 670         add_hook(&save_start_states, AFTER_DEF_HOOK);
 671         add_hook(&free_start_states, END_FUNC_HOOK);
 672         add_hook(&match_save_states, INLINE_FN_START);
 673         add_hook(&match_restore_states, INLINE_FN_END);
 674
 675         add_unmatched_state_hook(my_id, &empty_state);
 676         add_pre_merge_hook(my_id, &pre_merge_hook);
 677         add_merge_hook(my_id, &merge_estates);
 678
 679         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 680         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 681         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 682         for (i = 0; i < ARRAY_SIZE(kstr_funcs); i++)
 683                 add_function_hook(kstr_funcs[i], &match_user_copy, INT_PTR(2));
 684
 685         add_function_assign_hook("simple_strtol", &match_simple_strtoul, NULL);
 686         add_function_assign_hook("simple_strtoll", &match_simple_strtoul, NULL);
 687         add_function_assign_hook("simple_strtoul", &match_simple_strtoul, NULL);
 688         add_function_assign_hook("simple_strtoull", &match_simple_strtoul, NULL);
 689
 690         add_function_hook("sscanf", &match_sscanf, NULL);
 691
 692         add_function_assign_hook("memdup_user", &match_user_assign_function, NULL);
 693         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 694         add_function_assign_hook("skb_network_header", &match_user_assign_function, NULL);
 695
 696         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 697
 698         add_hook(&match_assign, ASSIGNMENT_HOOK);
 699
 700         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 701         add_member_info_callback(my_id, struct_member_callback);
 702         select_caller_info_hook(set_param_user_data, USER_DATA3);
 703         select_return_states_hook(USER_DATA3, &returns_param_user_data);
 704         add_split_return_callback(&param_set_to_user_data);
 705 }
 706
 707 void check_user_data3(int id)
 708 {
 709         my_call_id = id;
 710
 711         if (option_project != PROJ_KERNEL)
 712                 return;
 713         select_caller_info_hook(set_called, INTERNAL);
 714 }
 715