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