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