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 smatch_state *empty_state(struct sm_state *sm)
  35 {
  36         return alloc_estate_empty();
  37 }
  38
  39 static void tag_inner_struct_members(struct expression *expr, struct symbol *member)
  40 {
  41         struct expression *edge_member;
  42         struct symbol *base = get_real_base_type(member);
  43         struct symbol *tmp;
  44
  45         if (member->ident)
  46                 expr = member_expression(expr, '.', member->ident);
  47
  48         FOR_EACH_PTR(base->symbol_list, tmp) {
  49                 struct symbol *type;
  50
  51                 type = get_real_base_type(tmp);
  52                 if (!type)
  53                         continue;
  54
  55                 if (type->type == SYM_UNION || type->type == SYM_STRUCT) {
  56                         tag_inner_struct_members(expr, tmp);
  57                         continue;
  58                 }
  59
  60                 if (!tmp->ident)
  61                         continue;
  62
  63                 edge_member = member_expression(expr, '.', tmp->ident);
  64                 set_state_expr(my_id, edge_member, alloc_estate_whole(type));
  65         } END_FOR_EACH_PTR(tmp);
  66
  67
  68 }
  69
  70 static void tag_struct_members(struct symbol *type, struct expression *expr)
  71 {
  72         struct symbol *tmp;
  73         struct expression *member;
  74         int op = '*';
  75
  76         if (expr->type == EXPR_PREOP && expr->op == '&') {
  77                 expr = strip_expr(expr->unop);
  78                 op = '.';
  79         }
  80
  81         FOR_EACH_PTR(type->symbol_list, tmp) {
  82                 type = get_real_base_type(tmp);
  83                 if (!type)
  84                         continue;
  85
  86                 if (type->type == SYM_UNION || type->type == SYM_STRUCT) {
  87                         tag_inner_struct_members(expr, tmp);
  88                         continue;
  89                 }
  90
  91                 if (!tmp->ident)
  92                         continue;
  93
  94                 member = member_expression(expr, op, tmp->ident);
  95                 set_state_expr(my_id, member, alloc_estate_whole(get_type(member)));
  96         } END_FOR_EACH_PTR(tmp);
  97 }
  98
  99 static void tag_base_type(struct expression *expr)
 100 {
 101         if (expr->type == EXPR_PREOP && expr->op == '&')
 102                 expr = strip_expr(expr->unop);
 103         else
 104                 expr = deref_expression(expr);
 105         set_state_expr(my_id, expr, alloc_estate_whole(get_type(expr)));
 106 }
 107
 108 static void tag_as_user_data(struct expression *expr)
 109 {
 110         struct symbol *type;
 111
 112         expr = strip_expr(expr);
 113
 114         type = get_type(expr);
 115         if (!type || type->type != SYM_PTR)
 116                 return;
 117         type = get_real_base_type(type);
 118         if (!type)
 119                 return;
 120         if (type == &void_ctype) {
 121                 set_state_expr(my_id, deref_expression(expr), alloc_estate_whole(&ulong_ctype));
 122                 return;
 123         }
 124         if (type->type == SYM_BASETYPE)
 125                 tag_base_type(expr);
 126         if (type->type == SYM_STRUCT) {
 127                 if (expr->type != EXPR_PREOP || expr->op != '&')
 128                         expr = deref_expression(expr);
 129                 tag_struct_members(type, expr);
 130         }
 131 }
 132
 133 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 134 {
 135         int param = PTR_INT(_param);
 136         struct expression *dest;
 137
 138         dest = get_argument_from_call_expr(expr->args, param);
 139         dest = strip_expr(dest);
 140         if (!dest)
 141                 return;
 142         tag_as_user_data(dest);
 143 }
 144
 145 static int points_to_user_data(struct expression *expr)
 146 {
 147         struct smatch_state *state;
 148         char buf[256];
 149         struct symbol *sym;
 150         char *name;
 151         int ret = 0;
 152
 153         name = expr_to_var_sym(expr, &sym);
 154         if (!name || !sym)
 155                 goto free;
 156         snprintf(buf, sizeof(buf), "*%s", name);
 157         state = get_state(my_id, buf, sym);
 158         if (state && estate_rl(state))
 159                 ret = 1;
 160 free:
 161         free_string(name);
 162         return ret;
 163 }
 164
 165 static int is_skb_data(struct expression *expr)
 166 {
 167         struct symbol *sym;
 168
 169         expr = strip_expr(expr);
 170         if (!expr || expr->type != EXPR_DEREF)
 171                 return 0;
 172
 173         if (!expr->member)
 174                 return 0;
 175         if (strcmp(expr->member->name, "data") != 0)
 176                 return 0;
 177
 178         sym = expr_to_sym(expr->deref);
 179         if (!sym)
 180                 return 0;
 181         sym = get_real_base_type(sym);
 182         if (!sym || sym->type != SYM_PTR)
 183                 return 0;
 184         sym = get_real_base_type(sym);
 185         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 186                 return 0;
 187         if (strcmp(sym->ident->name, "sk_buff") != 0)
 188                 return 0;
 189
 190         return 1;
 191 }
 192
 193 static int comes_from_skb_data(struct expression *expr)
 194 {
 195         expr = strip_expr(expr);
 196         if (!expr)
 197                 return 0;
 198
 199         return 0;
 200         switch (expr->type) {
 201         case EXPR_BINOP:
 202                 if (comes_from_skb_data(expr->left))
 203                         return 1;
 204                 if (comes_from_skb_data(expr->right))
 205                         return 1;
 206                 return 0;
 207         case EXPR_PREOP:
 208                 return comes_from_skb_data(expr->unop);
 209         case EXPR_DEREF:
 210                 if (is_skb_data(expr))
 211                         return 1;
 212                 return comes_from_skb_data(expr->deref);
 213         default:
 214                 return 0;
 215         }
 216 }
 217
 218
 219 static int handle_struct_assignment(struct expression *expr)
 220 {
 221         struct expression *right;
 222         struct symbol *type;
 223
 224         type = get_type(expr->left);
 225         if (!type || type->type != SYM_PTR)
 226                 return 0;
 227         type = get_real_base_type(type);
 228         if (!type || type->type != SYM_STRUCT)
 229                 return 0;
 230
 231         /*
 232          * Ignore struct to struct assignments because for those we look at the
 233          * individual members.
 234          */
 235         right = strip_expr(expr->right);
 236         type = get_type(right);
 237         if (!type || type->type != SYM_PTR)
 238                 return 0;
 239         type = get_real_base_type(type);
 240         if (type && type->type == SYM_STRUCT)
 241                 return 0;
 242
 243         if (!points_to_user_data(right) && !is_skb_data(right))
 244                 return 0;
 245
 246         tag_as_user_data(expr->left);
 247         return 1;
 248 }
 249
 250 static int handle_get_user(struct expression *expr)
 251 {
 252         char *name;
 253         int ret = 0;
 254
 255         name = get_macro_name(expr->pos);
 256         if (!name || strcmp(name, "get_user") != 0)
 257                 return 0;
 258
 259         name = expr_to_var(expr->right);
 260         if (!name || strcmp(name, "__val_gu") != 0)
 261                 goto free;
 262         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 263         ret = 1;
 264 free:
 265         free_string(name);
 266         return ret;
 267 }
 268
 269 static void match_assign(struct expression *expr)
 270 {
 271         struct range_list *rl;
 272
 273         if (is_fake_call(expr->right))
 274                 return;
 275         if (handle_struct_assignment(expr))
 276                 return;
 277         if (handle_get_user(expr))
 278                 return;
 279
 280         if (expr->right->type == EXPR_CALL ||
 281             !get_user_rl(expr->right, &rl))
 282                 goto clear_old_state;
 283
 284         rl = cast_rl(get_type(expr->left), rl);
 285         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 286
 287         return;
 288
 289 clear_old_state:
 290         if (get_state_expr(my_id, expr->left))
 291                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 292 }
 293
 294 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 295 {
 296         tag_as_user_data(expr->left);
 297 }
 298
 299 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 300 {
 301         char *macro;
 302
 303         if (!expr)
 304                 return 0;
 305         macro = get_macro_name(expr->pos);
 306
 307         if (!macro)
 308                 return 0;
 309
 310         if (strcmp(macro, "ntohl") == 0) {
 311                 *rl = alloc_whole_rl(&uint_ctype);
 312                 return 1;
 313         }
 314         if (strcmp(macro, "ntohs") == 0) {
 315                 *rl = alloc_whole_rl(&ushort_ctype);
 316                 return 1;
 317         }
 318         return 0;
 319 }
 320
 321 static int user_data_flag;
 322 static struct range_list *var_user_rl(struct expression *expr)
 323 {
 324         struct smatch_state *state;
 325         struct range_list *rl;
 326         struct range_list *absolute_rl;
 327
 328         if (get_user_macro_rl(expr, &rl))
 329                 goto found;
 330
 331         if (comes_from_skb_data(expr)) {
 332                 rl = alloc_whole_rl(get_type(expr));
 333                 goto found;
 334         }
 335
 336         state = get_state_expr(my_id, expr);
 337         if (state && estate_rl(state)) {
 338                 rl = estate_rl(state);
 339                 goto found;
 340         }
 341
 342         return NULL;
 343 found:
 344         user_data_flag = 1;
 345         absolute_rl = var_to_absolute_rl(expr);
 346         if (local_debug) {
 347                 sm_msg("user rl = '%s'.  absolute = '%s'.  intersection = '%s'",
 348                        show_rl(rl), show_rl(absolute_rl), show_rl((rl_intersection(rl, absolute_rl))));
 349         }
 350         return clone_rl(rl_intersection(rl, absolute_rl));
 351 }
 352
 353 int get_user_rl(struct expression *expr, struct range_list **rl)
 354 {
 355
 356         user_data_flag = 0;
 357         custom_get_absolute_rl(expr, &var_user_rl, rl);
 358         if (!user_data_flag) {
 359                 *rl = NULL;
 360                 return 0;
 361         }
 362         return 1;
 363 }
 364
 365 static void match_call_info(struct expression *expr)
 366 {
 367         struct range_list *rl;
 368         struct expression *arg;
 369         int i = 0;
 370
 371         i = -1;
 372         FOR_EACH_PTR(expr->args, arg) {
 373                 i++;
 374
 375                 if (!get_user_rl(arg, &rl))
 376                         continue;
 377
 378                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 379                 i++;
 380         } END_FOR_EACH_PTR(arg);
 381 }
 382
 383 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 384 {
 385         struct smatch_state *state;
 386         struct range_list *rl;
 387
 388         if (strcmp(sm->state->name, "") == 0)
 389                 return;
 390
 391         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 392         if (!state || !estate_rl(state))
 393                 rl = estate_rl(sm->state);
 394         else
 395                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 396
 397         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 398 }
 399
 400 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 401 {
 402         struct range_list *rl = NULL;
 403         struct smatch_state *state;
 404         struct symbol *type;
 405         char fullname[256];
 406
 407         if (strcmp(key, "*$") == 0)
 408                 snprintf(fullname, sizeof(fullname), "*%s", name);
 409         else if (strncmp(key, "$", 1) == 0)
 410                 snprintf(fullname, 256, "%s%s", name, key + 1);
 411         else
 412                 return;
 413
 414         type = get_member_type_from_key(symbol_expression(sym), key);
 415
 416         /* if the caller passes a void pointer with user data */
 417         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 418                 struct expression *expr = symbol_expression(sym);
 419
 420                 tag_as_user_data(expr);
 421                 return;
 422         }
 423         str_to_rl(type, value, &rl);
 424         state = alloc_estate_rl(rl);
 425         set_state(my_id, fullname, sym, state);
 426 }
 427
 428 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 429 {
 430         set_state(my_call_id, "this_function", NULL, &called);
 431 }
 432
 433 static void match_syscall_definition(struct symbol *sym)
 434 {
 435         struct symbol *arg;
 436         char *macro;
 437         char *name;
 438         int is_syscall = 0;
 439
 440         macro = get_macro_name(sym->pos);
 441         if (macro &&
 442             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 443              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 444                 is_syscall = 1;
 445
 446         name = get_function();
 447         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 448                 if (name && strncmp(name, "sys_", 4) == 0)
 449                         is_syscall = 1;
 450         }
 451
 452         if (name && strncmp(name, "compat_sys_", 11) == 0)
 453                 is_syscall = 1;
 454
 455         if (!is_syscall)
 456                 return;
 457
 458         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 459                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 460         } END_FOR_EACH_PTR(arg);
 461 }
 462
 463 void check_user_data2(int id)
 464 {
 465         my_id = id;
 466
 467         if (option_project != PROJ_KERNEL)
 468                 return;
 469
 470         add_unmatched_state_hook(my_id, &empty_state);
 471         add_merge_hook(my_id, &merge_estates);
 472
 473         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 474         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 475         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 476         add_function_hook("_kstrtoull", &match_user_copy, INT_PTR(2));
 477
 478         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 479         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 480
 481         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 482
 483         add_hook(&match_assign, ASSIGNMENT_HOOK);
 484
 485         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 486         add_member_info_callback(my_id, struct_member_callback);
 487         select_caller_info_hook(set_param_user_data, USER_DATA3);
 488 }
 489
 490 void check_user_data3(int id)
 491 {
 492         my_call_id = id;
 493
 494         if (option_project != PROJ_KERNEL)
 495                 return;
 496         select_caller_info_hook(set_called, INTERNAL);
 497 }
 498