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