check_user_data.c

   1 /*
   2  * smatch/check_user_data.c
   3  *
   4  * Copyright (C) 2011 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * There are a couple checks that try to see if a variable
  12  * comes from the user.  It would be better to unify them
  13  * into one place.  Also it we should follow the data down
  14  * the call paths.  Hence this file.
  15  */
  16
  17 #include "smatch.h"
  18 #include "smatch_slist.h"
  19 #include "smatch_extra.h"
  20
  21 void tag_as_user_data(struct expression *expr);
  22
  23 static int my_id;
  24
  25 STATE(capped);
  26 STATE(user_data_passed);
  27 STATE(user_data_set);
  28
  29 enum {
  30         SET_DATA = 1,
  31         PASSED_DATA = 2,
  32 };
  33
  34 static int is_user_macro(struct expression *expr)
  35 {
  36         return 0;
  37 }
  38
  39 static int has_user_data_state(struct expression *expr, struct state_list *my_slist)
  40 {
  41         struct sm_state *sm;
  42         struct symbol *sym;
  43         char *name;
  44
  45         expr = strip_expr(expr);
  46         if (expr->type == EXPR_PREOP && expr->op == '&')
  47                 expr = strip_expr(expr->unop);
  48
  49         name = expr_to_str_sym(expr, &sym);
  50         free_string(name);
  51         if (!sym)
  52                 return 1;
  53
  54         FOR_EACH_PTR(my_slist, sm) {
  55                 if (sm->sym == sym)
  56                         return 1;
  57         } END_FOR_EACH_PTR(sm);
  58         return 0;
  59 }
  60
  61 static int passes_user_data(struct expression *expr)
  62 {
  63         struct state_list *slist;
  64         struct expression *arg;
  65
  66         slist = get_all_states(my_id);
  67         FOR_EACH_PTR(expr->args, arg) {
  68                 if (is_user_data(arg))
  69                         return 1;
  70                 if (has_user_data_state(arg, slist))
  71                         return 1;
  72         } END_FOR_EACH_PTR(arg);
  73
  74         return 0;
  75 }
  76
  77 static struct expression *db_expr;
  78 static int db_user_data;
  79 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
  80 {
  81         if (atoi(argv[0]) == PASSED_DATA && !passes_user_data(db_expr))
  82                 return 0;
  83         db_user_data = 1;
  84         return 0;
  85 }
  86
  87 static int is_user_fn_db(struct expression *expr)
  88 {
  89         struct symbol *sym;
  90         static char sql_filter[1024];
  91
  92         if (expr->fn->type != EXPR_SYMBOL)
  93                 return 0;
  94         sym = expr->fn->symbol;
  95         if (!sym)
  96                 return 0;
  97
  98         if (sym->ctype.modifiers & MOD_STATIC) {
  99                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
 100                          get_filename(), sym->ident->name);
 101         } else {
 102                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
 103                                 sym->ident->name);
 104         }
 105
 106         db_expr = expr;
 107         db_user_data = 0;
 108         run_sql(db_user_data_callback,
 109                 "select value from return_states where type=%d and parameter = -1 and key = '$$' and %s",
 110                 USER_DATA, sql_filter);
 111         return db_user_data;
 112 }
 113
 114 static int is_user_function(struct expression *expr)
 115 {
 116         if (expr->type != EXPR_CALL)
 117                 return 0;
 118         if (sym_name_is("kmemdup_user", expr->fn))
 119                 return SET_DATA;
 120         return is_user_fn_db(expr);
 121 }
 122
 123 static int is_skb_data(struct expression *expr)
 124 {
 125         struct symbol *sym;
 126         char *name;
 127         int len;
 128         int ret = 0;
 129
 130         name = expr_to_var_sym(expr, &sym);
 131         if (!name || !sym)
 132                 goto free;
 133
 134         sym = get_base_type(sym);
 135         if (!sym || sym->type != SYM_PTR)
 136                 goto free;
 137         sym = get_base_type(sym);
 138         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 139                 goto free;
 140         if (strcmp(sym->ident->name, "sk_buff") != 0)
 141                 goto free;
 142
 143         len = strlen(name);
 144         if (len < 6)
 145                 goto free;
 146         if (strcmp(name + len - 6, "->data") == 0)
 147                 ret = SET_DATA;
 148
 149 free:
 150         free_string(name);
 151         return ret;
 152 }
 153
 154 static int in_container_of_macro(struct expression *expr)
 155 {
 156         char *macro;
 157
 158         macro = get_macro_name(expr->pos);
 159
 160         if (!macro)
 161                 return 0;
 162         if (strcmp(macro, "container_of") == 0)
 163                 return 1;
 164         return 0;
 165 }
 166
 167 static int is_user_data_state(struct expression *expr)
 168 {
 169         struct state_list *slist = NULL;
 170         struct sm_state *tmp;
 171         struct symbol *sym;
 172         char *name;
 173         int user = 0;
 174
 175         tmp = get_sm_state_expr(my_id, expr);
 176         if (tmp) {
 177                 if (slist_has_state(tmp->possible, &user_data_set))
 178                         return SET_DATA;
 179                 if (slist_has_state(tmp->possible, &user_data_passed))
 180                         return PASSED_DATA;
 181                 return 0;
 182         }
 183
 184         name = expr_to_str_sym(expr, &sym);
 185         if (!name || !sym)
 186                 goto free;
 187
 188         slist = get_all_states(my_id);
 189         FOR_EACH_PTR(slist, tmp) {
 190                 if (tmp->sym != sym)
 191                         continue;
 192                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 193                         if (slist_has_state(tmp->possible, &user_data_set))
 194                                 user = SET_DATA;
 195                         else if (slist_has_state(tmp->possible, &user_data_passed))
 196                                 user = PASSED_DATA;
 197                         goto free;
 198                 }
 199         } END_FOR_EACH_PTR(tmp);
 200
 201 free:
 202         free_slist(&slist);
 203         free_string(name);
 204         return user;
 205 }
 206
 207 int is_user_data(struct expression *expr)
 208 {
 209         int user_data;
 210
 211         if (!expr)
 212                 return 0;
 213
 214         if (is_capped(expr))
 215                 return 0;
 216         if (in_container_of_macro(expr))
 217                 return 0;
 218
 219         user_data = is_user_macro(expr);
 220         if (user_data)
 221                 return user_data;
 222         user_data = is_user_function(expr);
 223         if (user_data)
 224                 return user_data;
 225         user_data = is_skb_data(expr);
 226         if (user_data)
 227                 return user_data;
 228
 229         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 230
 231         if (expr->type == EXPR_BINOP) {
 232                 user_data = is_user_data(expr->left);
 233                 if (user_data)
 234                         return user_data;
 235                 if (is_array(expr))
 236                         return 0;
 237                 user_data = is_user_data(expr->right);
 238                 if (user_data)
 239                         return user_data;
 240                 return 0;
 241         }
 242         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 243                 expr = strip_expr(expr->unop);
 244
 245         return is_user_data_state(expr);
 246 }
 247
 248 int is_capped_user_data(struct expression *expr)
 249 {
 250         struct sm_state *sm;
 251
 252         sm = get_sm_state_expr(my_id, expr);
 253         if (!sm)
 254                 return 0;
 255         if (slist_has_state(sm->possible, &capped))
 256                 return 1;
 257         return 0;
 258 }
 259
 260 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 261 {
 262         char fullname[256];
 263
 264         /* sanity check.  this should always be true. */
 265         if (strncmp(key, "$$", 2) != 0)
 266                 return;
 267         snprintf(fullname, 256, "%s%s", name, key + 2);
 268         set_state(my_id, fullname, sym, &user_data_passed);
 269 }
 270
 271 static void match_syscall_definition(struct symbol *sym)
 272 {
 273         struct symbol *arg;
 274         char *macro;
 275
 276         macro = get_macro_name(sym->pos);
 277         if (!macro)
 278                 return;
 279         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 280             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 281                 return;
 282
 283         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 284                 set_state(my_id, arg->ident->name, arg, &user_data_set);
 285         } END_FOR_EACH_PTR(arg);
 286 }
 287
 288 static void match_condition(struct expression *expr)
 289 {
 290         switch (expr->op) {
 291         case '<':
 292         case SPECIAL_LTE:
 293         case SPECIAL_UNSIGNED_LT:
 294         case SPECIAL_UNSIGNED_LTE:
 295                 if (is_user_data(expr->left))
 296                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 297                 if (is_user_data(expr->right))
 298                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 299                 break;
 300         case '>':
 301         case SPECIAL_GTE:
 302         case SPECIAL_UNSIGNED_GT:
 303         case SPECIAL_UNSIGNED_GTE:
 304                 if (is_user_data(expr->right))
 305                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 306                 if (is_user_data(expr->left))
 307                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 308                 break;
 309         case SPECIAL_EQUAL:
 310                 if (is_user_data(expr->left))
 311                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 312                 if (is_user_data(expr->right))
 313                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 314                 break;
 315         case SPECIAL_NOTEQUAL:
 316                 if (is_user_data(expr->left))
 317                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 318                 if (is_user_data(expr->right))
 319                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 320                 break;
 321         default:
 322                 return;
 323         }
 324 }
 325
 326 static void set_capped(struct sm_state *sm, struct expression *mod_expr)
 327 {
 328         set_state(my_id, sm->name, sm->sym, &capped);
 329 }
 330
 331 static void match_normal_assign(struct expression *expr)
 332 {
 333         int user_data;
 334
 335         user_data = is_user_data(expr->right);
 336         if (user_data == PASSED_DATA)
 337                 set_state_expr(my_id, expr->left, &user_data_passed);
 338         if (user_data == SET_DATA)
 339                 set_state_expr(my_id, expr->left, &user_data_set);
 340 }
 341
 342 static void match_assign(struct expression *expr)
 343 {
 344         char *name;
 345
 346         name = get_macro_name(expr->pos);
 347         if (!name || strcmp(name, "get_user") != 0) {
 348                 match_normal_assign(expr);
 349                 return;
 350         }
 351         name = expr_to_var(expr->right);
 352         if (!name || strcmp(name, "__val_gu") != 0)
 353                 goto free;
 354         set_state_expr(my_id, expr->left, &user_data_set);
 355 free:
 356         free_string(name);
 357 }
 358
 359 static void tag_struct_members(struct symbol *type, struct expression *expr)
 360 {
 361         struct symbol *tmp;
 362         struct expression *member;
 363         int op = '*';
 364
 365         if (expr->type == EXPR_PREOP && expr->op == '&') {
 366                 expr = strip_expr(expr->unop);
 367                 op = '.';
 368         }
 369
 370         FOR_EACH_PTR(type->symbol_list, tmp) {
 371                 if (!tmp->ident)
 372                         continue;
 373                 member = member_expression(expr, op, tmp->ident);
 374                 set_state_expr(my_id, member, &user_data_set);
 375         } END_FOR_EACH_PTR(tmp);
 376 }
 377
 378 static void tag_base_type(struct expression *expr)
 379 {
 380         if (expr->type == EXPR_PREOP && expr->op == '&')
 381                 expr = strip_expr(expr->unop);
 382         else
 383                 expr = deref_expression(expr);
 384         set_state_expr(my_id, expr, &user_data_set);
 385 }
 386
 387 void tag_as_user_data(struct expression *expr)
 388 {
 389         struct symbol *type;
 390
 391         expr = strip_expr(expr);
 392
 393         type = get_type(expr);
 394         if (!type || type->type != SYM_PTR)
 395                 return;
 396         type = get_real_base_type(type);
 397         if (!type)
 398                 return;
 399         if (type == &void_ctype) {
 400                 set_state_expr(my_id, deref_expression(expr), &user_data_set);
 401                 return;
 402         }
 403         if (type->type == SYM_BASETYPE)
 404                 tag_base_type(expr);
 405         if (type->type == SYM_STRUCT) {
 406                 if (expr->type != EXPR_PREOP || expr->op != '&')
 407                         expr = deref_expression(expr);
 408                 tag_struct_members(type, expr);
 409         }
 410 }
 411
 412 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 413 {
 414         int param = PTR_INT(_param);
 415         struct expression *dest;
 416
 417         dest = get_argument_from_call_expr(expr->args, param);
 418         dest = strip_expr(dest);
 419         if (!dest)
 420                 return;
 421         tag_as_user_data(dest);
 422 }
 423
 424 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 425 {
 426         set_state_expr(my_id, expr->left, &user_data_set);
 427 }
 428
 429 static void match_macro_assign(const char *fn, struct expression *expr, void *_bits)
 430 {
 431         int bits;
 432
 433         bits = nr_bits(expr->left);
 434         if (!bits)
 435                 return;
 436         if (bits > nr_bits(expr->right))
 437                 return;
 438         set_state_expr(my_id, expr->left, &user_data_set);
 439 }
 440
 441 static void match_caller_info(struct expression *expr)
 442 {
 443         struct expression *tmp;
 444         int i;
 445
 446         i = 0;
 447         FOR_EACH_PTR(expr->args, tmp) {
 448                 if (is_user_data(tmp))
 449                         sql_insert_caller_info(expr, USER_DATA, i, "$$", "");
 450                 i++;
 451         } END_FOR_EACH_PTR(tmp);
 452 }
 453
 454 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 455 {
 456         if (state == &capped)
 457                 return;
 458         sql_insert_caller_info(call, USER_DATA, param, printed_name, "");
 459 }
 460
 461 static void returned_member_callback(int return_id, char *return_ranges, char *printed_name, struct smatch_state *state)
 462 {
 463         if (state == &capped)
 464                 return;
 465         sql_insert_return_states(return_id, return_ranges, USER_DATA, -1, printed_name, "");
 466 }
 467
 468 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 469 {
 470         struct state_list *my_slist;
 471         struct sm_state *tmp;
 472         int param;
 473         int user_data;
 474         const char *passed_or_new;
 475
 476         user_data = is_user_data(expr);
 477         if (user_data == PASSED_DATA) {
 478                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 479                                 -1, "$$", "2");
 480         }
 481         if (user_data == SET_DATA) {
 482                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 483                                 -1, "$$", "1");
 484         }
 485
 486         my_slist = get_all_states(my_id);
 487
 488         FOR_EACH_PTR(my_slist, tmp) {
 489                 const char *param_name;
 490
 491                 param = get_param_num_from_sym(tmp->sym);
 492                 if (param < 0)
 493                         continue;
 494
 495                 if (is_capped_var_sym(tmp->name, tmp->sym))
 496                         continue;
 497                 /* ignore states that were already USER_DATA to begin with */
 498                 if (get_state_slist(get_start_states(), my_id, tmp->name, tmp->sym))
 499                         continue;
 500
 501                 param_name = get_param_name(tmp);
 502                 if (!param_name)
 503                         return;
 504
 505                 if (slist_has_state(tmp->possible, &user_data_set))
 506                         passed_or_new = "1";
 507                 if (slist_has_state(tmp->possible, &user_data_passed))
 508                         passed_or_new = "2";
 509
 510                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 511                                 param, param_name, passed_or_new);
 512         } END_FOR_EACH_PTR(tmp);
 513
 514         free_slist(&my_slist);
 515 }
 516
 517 static void db_return_states_userdata(struct expression *expr, int param, char *key, char *value)
 518 {
 519         char *name;
 520         struct symbol *sym;
 521
 522         name = return_state_to_var_sym(expr, param, key, &sym);
 523         if (!name || !sym)
 524                 goto free;
 525
 526         set_state(my_id, name, sym, &user_data_set);
 527 free:
 528         free_string(name);
 529 }
 530
 531 void check_user_data(int id)
 532 {
 533         if (option_project != PROJ_KERNEL)
 534                 return;
 535         my_id = id;
 536         select_caller_info_hook(set_param_user_data, USER_DATA);
 537         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 538         add_hook(&match_condition, CONDITION_HOOK);
 539         add_hook(&match_assign, ASSIGNMENT_HOOK);
 540         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 541         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 542         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 543         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 544
 545         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 546         add_member_info_callback(my_id, struct_member_callback);
 547         add_returned_member_callback(my_id, returned_member_callback);
 548         add_returned_state_callback(print_returned_user_data);
 549         select_return_states_hook(USER_DATA, &db_return_states_userdata);
 550
 551         add_modification_hook(my_id, &set_capped);
 552 }