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         name = expr_to_var_sym(expr, &sym);
 192         if (!name || !sym)
 193                 goto free;
 194         snprintf(buf, sizeof(buf), "*%s", name);
 195         state = get_state(my_id, buf, sym);
 196         if (state && estate_rl(state))
 197                 ret = 1;
 198 free:
 199         free_string(name);
 200         return ret;
 201 }
 202
 203 static int is_skb_data(struct expression *expr)
 204 {
 205         struct symbol *sym;
 206
 207         expr = strip_expr(expr);
 208         if (!expr || expr->type != EXPR_DEREF)
 209                 return 0;
 210
 211         if (!expr->member)
 212                 return 0;
 213         if (strcmp(expr->member->name, "data") != 0)
 214                 return 0;
 215
 216         sym = expr_to_sym(expr->deref);
 217         if (!sym)
 218                 return 0;
 219         sym = get_real_base_type(sym);
 220         if (!sym || sym->type != SYM_PTR)
 221                 return 0;
 222         sym = get_real_base_type(sym);
 223         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 224                 return 0;
 225         if (strcmp(sym->ident->name, "sk_buff") != 0)
 226                 return 0;
 227
 228         return 1;
 229 }
 230
 231 static int comes_from_skb_data(struct expression *expr)
 232 {
 233         expr = strip_expr(expr);
 234         if (!expr)
 235                 return 0;
 236
 237         switch (expr->type) {
 238         case EXPR_BINOP:
 239                 if (comes_from_skb_data(expr->left))
 240                         return 1;
 241                 if (comes_from_skb_data(expr->right))
 242                         return 1;
 243                 return 0;
 244         case EXPR_PREOP:
 245                 return comes_from_skb_data(expr->unop);
 246         case EXPR_DEREF:
 247                 if (is_skb_data(expr))
 248                         return 1;
 249                 return comes_from_skb_data(expr->deref);
 250         default:
 251                 return 0;
 252         }
 253 }
 254
 255
 256 static int handle_struct_assignment(struct expression *expr)
 257 {
 258         struct expression *right;
 259         struct symbol *type;
 260
 261         type = get_type(expr->left);
 262         if (!type || type->type != SYM_PTR)
 263                 return 0;
 264         type = get_real_base_type(type);
 265         if (!type || type->type != SYM_STRUCT)
 266                 return 0;
 267
 268         /*
 269          * Ignore struct to struct assignments because for those we look at the
 270          * individual members.
 271          */
 272         right = strip_expr(expr->right);
 273         type = get_type(right);
 274         if (!type || type->type != SYM_PTR)
 275                 return 0;
 276         type = get_real_base_type(type);
 277         if (type && type->type == SYM_STRUCT)
 278                 return 0;
 279
 280         if (!points_to_user_data(right) && !is_skb_data(right))
 281                 return 0;
 282
 283         tag_as_user_data(expr->left);
 284         return 1;
 285 }
 286
 287 static int handle_get_user(struct expression *expr)
 288 {
 289         char *name;
 290         int ret = 0;
 291
 292         name = get_macro_name(expr->pos);
 293         if (!name || strcmp(name, "get_user") != 0)
 294                 return 0;
 295
 296         name = expr_to_var(expr->right);
 297         if (!name || strcmp(name, "__val_gu") != 0)
 298                 goto free;
 299         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 300         ret = 1;
 301 free:
 302         free_string(name);
 303         return ret;
 304 }
 305
 306 static void match_assign(struct expression *expr)
 307 {
 308         struct range_list *rl;
 309
 310         if (is_fake_call(expr->right))
 311                 return;
 312         if (handle_struct_assignment(expr))
 313                 return;
 314         if (handle_get_user(expr))
 315                 return;
 316
 317         if (expr->right->type == EXPR_CALL ||
 318             !get_user_rl(expr->right, &rl))
 319                 goto clear_old_state;
 320
 321         rl = cast_rl(get_type(expr->left), rl);
 322         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 323
 324         return;
 325
 326 clear_old_state:
 327         if (get_state_expr(my_id, expr->left))
 328                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 329 }
 330
 331 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 332 {
 333         tag_as_user_data(expr->left);
 334 }
 335
 336 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 337 {
 338         char *macro;
 339
 340         if (!expr)
 341                 return 0;
 342         macro = get_macro_name(expr->pos);
 343
 344         if (!macro)
 345                 return 0;
 346
 347         if (strcmp(macro, "ntohl") == 0) {
 348                 *rl = alloc_whole_rl(&uint_ctype);
 349                 return 1;
 350         }
 351         if (strcmp(macro, "ntohs") == 0) {
 352                 *rl = alloc_whole_rl(&ushort_ctype);
 353                 return 1;
 354         }
 355         return 0;
 356 }
 357
 358 static int user_data_flag;
 359 static struct range_list *var_user_rl(struct expression *expr)
 360 {
 361         struct smatch_state *state;
 362         struct range_list *rl;
 363         struct range_list *absolute_rl;
 364
 365         if (get_user_macro_rl(expr, &rl))
 366                 goto found;
 367
 368         if (comes_from_skb_data(expr)) {
 369                 rl = alloc_whole_rl(get_type(expr));
 370                 goto found;
 371         }
 372
 373         state = get_state_expr(my_id, expr);
 374         if (state && estate_rl(state)) {
 375                 rl = estate_rl(state);
 376                 goto found;
 377         }
 378
 379         return NULL;
 380 found:
 381         user_data_flag = 1;
 382         absolute_rl = var_to_absolute_rl(expr);
 383         return clone_rl(rl_intersection(rl, absolute_rl));
 384 }
 385
 386 int get_user_rl(struct expression *expr, struct range_list **rl)
 387 {
 388
 389         user_data_flag = 0;
 390         custom_get_absolute_rl(expr, &var_user_rl, rl);
 391         if (!user_data_flag) {
 392                 *rl = NULL;
 393                 return 0;
 394         }
 395         return 1;
 396 }
 397
 398 static void match_call_info(struct expression *expr)
 399 {
 400         struct range_list *rl;
 401         struct expression *arg;
 402         int i = 0;
 403
 404         i = -1;
 405         FOR_EACH_PTR(expr->args, arg) {
 406                 i++;
 407
 408                 if (!get_user_rl(arg, &rl))
 409                         continue;
 410
 411                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 412         } END_FOR_EACH_PTR(arg);
 413 }
 414
 415 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 416 {
 417         struct smatch_state *state;
 418         struct range_list *rl;
 419
 420         if (strcmp(sm->state->name, "") == 0)
 421                 return;
 422
 423         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 424         if (!state || !estate_rl(state))
 425                 rl = estate_rl(sm->state);
 426         else
 427                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 428
 429         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 430 }
 431
 432 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 433 {
 434         struct range_list *rl = NULL;
 435         struct smatch_state *state;
 436         struct symbol *type;
 437         char fullname[256];
 438
 439         if (strcmp(key, "*$") == 0)
 440                 snprintf(fullname, sizeof(fullname), "*%s", name);
 441         else if (strncmp(key, "$", 1) == 0)
 442                 snprintf(fullname, 256, "%s%s", name, key + 1);
 443         else
 444                 return;
 445
 446         type = get_member_type_from_key(symbol_expression(sym), key);
 447
 448         /* if the caller passes a void pointer with user data */
 449         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 450                 struct expression *expr = symbol_expression(sym);
 451
 452                 tag_as_user_data(expr);
 453                 return;
 454         }
 455         str_to_rl(type, value, &rl);
 456         state = alloc_estate_rl(rl);
 457         set_state(my_id, fullname, sym, state);
 458 }
 459
 460 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 461 {
 462         set_state(my_call_id, "this_function", NULL, &called);
 463 }
 464
 465 static void match_syscall_definition(struct symbol *sym)
 466 {
 467         struct symbol *arg;
 468         char *macro;
 469         char *name;
 470         int is_syscall = 0;
 471
 472         macro = get_macro_name(sym->pos);
 473         if (macro &&
 474             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 475              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 476                 is_syscall = 1;
 477
 478         name = get_function();
 479         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 480                 if (name && strncmp(name, "sys_", 4) == 0)
 481                         is_syscall = 1;
 482         }
 483
 484         if (name && strncmp(name, "compat_sys_", 11) == 0)
 485                 is_syscall = 1;
 486
 487         if (!is_syscall)
 488                 return;
 489
 490         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 491                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 492         } END_FOR_EACH_PTR(arg);
 493 }
 494
 495 static void returns_param_user_data(struct expression *expr, int param, char *key, char *value)
 496 {
 497         struct expression *arg;
 498         char *name;
 499         struct symbol *sym;
 500         struct symbol *type;
 501         struct range_list *rl = NULL;
 502
 503         while (expr->type == EXPR_ASSIGNMENT)
 504                 expr = strip_expr(expr->right);
 505         if (expr->type != EXPR_CALL)
 506                 return;
 507
 508         arg = get_argument_from_call_expr(expr->args, param);
 509         if (!arg)
 510                 return;
 511         type = get_member_type_from_key(arg, key);
 512         name = get_variable_from_key(arg, key, &sym);
 513         if (!name || !sym)
 514                 goto free;
 515
 516         call_results_to_rl(expr, type, value, &rl);
 517
 518         set_state(my_id, name, sym, alloc_estate_rl(rl));
 519 free:
 520         free_string(name);
 521 }
 522
 523 static int has_empty_state(struct sm_state *sm)
 524 {
 525         struct sm_state *tmp;
 526
 527         FOR_EACH_PTR(sm->possible, tmp) {
 528                 if (!estate_rl(tmp->state))
 529                         return 1;
 530         } END_FOR_EACH_PTR(tmp);
 531
 532         return 0;
 533 }
 534
 535 static void param_set_to_user_data(int return_id, char *return_ranges, struct expression *expr)
 536 {
 537         struct sm_state *sm;
 538         struct smatch_state *start_state;
 539         int param;
 540         const char *param_name;
 541
 542         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 543                 if (has_empty_state(sm))
 544                         continue;
 545
 546
 547                 param = get_param_num_from_sym(sm->sym);
 548                 if (param < 0) {
 549                         if (expr_to_sym(expr) == sm->sym)
 550                                 param = -1;
 551                         else
 552                                 continue;
 553                 }
 554
 555
 556                 start_state = get_state_stree(start_states, my_id, sm->name, sm->sym);
 557                 if (start_state && estates_equiv(sm->state, start_state))
 558                         continue;
 559
 560
 561                 param_name = get_param_name(sm);
 562                 if (!param_name)
 563                         continue;
 564                 if (strcmp(param_name, "$") == 0)
 565                         continue;
 566
 567                 sql_insert_return_states(return_id, return_ranges, USER_DATA3,
 568                                          param, param_name, show_rl(estate_rl(sm->state)));
 569         } END_FOR_EACH_SM(sm);
 570 }
 571
 572 void check_user_data2(int id)
 573 {
 574         my_id = id;
 575
 576         if (option_project != PROJ_KERNEL)
 577                 return;
 578
 579         add_hook(&save_start_states, AFTER_DEF_HOOK);
 580         add_hook(&free_start_states, END_FUNC_HOOK);
 581         add_hook(&match_save_states, INLINE_FN_START);
 582         add_hook(&match_restore_states, INLINE_FN_END);
 583
 584         add_unmatched_state_hook(my_id, &empty_state);
 585         add_merge_hook(my_id, &merge_estates);
 586
 587         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 588         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 589         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 590         add_function_hook("_kstrtoull", &match_user_copy, INT_PTR(2));
 591
 592         add_function_hook("sscanf", &match_sscanf, NULL);
 593
 594         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 595         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 596
 597         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 598
 599         add_hook(&match_assign, ASSIGNMENT_HOOK);
 600
 601         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 602         add_member_info_callback(my_id, struct_member_callback);
 603         select_caller_info_hook(set_param_user_data, USER_DATA3);
 604         select_return_states_hook(USER_DATA3, &returns_param_user_data);
 605         add_split_return_callback(&param_set_to_user_data);
 606 }
 607
 608 void check_user_data3(int id)
 609 {
 610         my_call_id = id;
 611
 612         if (option_project != PROJ_KERNEL)
 613                 return;
 614         select_caller_info_hook(set_called, INTERNAL);
 615 }
 616