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         switch (expr->type) {
 200         case EXPR_BINOP:
 201                 if (comes_from_skb_data(expr->left))
 202                         return 1;
 203                 if (comes_from_skb_data(expr->right))
 204                         return 1;
 205                 return 0;
 206         case EXPR_PREOP:
 207                 return comes_from_skb_data(expr->unop);
 208         case EXPR_DEREF:
 209                 if (is_skb_data(expr))
 210                         return 1;
 211                 return comes_from_skb_data(expr->deref);
 212         default:
 213                 return 0;
 214         }
 215 }
 216
 217
 218 static int handle_struct_assignment(struct expression *expr)
 219 {
 220         struct expression *right;
 221         struct symbol *type;
 222
 223         type = get_type(expr->left);
 224         if (!type || type->type != SYM_PTR)
 225                 return 0;
 226         type = get_real_base_type(type);
 227         if (!type || type->type != SYM_STRUCT)
 228                 return 0;
 229
 230         /*
 231          * Ignore struct to struct assignments because for those we look at the
 232          * individual members.
 233          */
 234         right = strip_expr(expr->right);
 235         type = get_type(right);
 236         if (!type || type->type != SYM_PTR)
 237                 return 0;
 238         type = get_real_base_type(type);
 239         if (type && type->type == SYM_STRUCT)
 240                 return 0;
 241
 242         if (!points_to_user_data(right) && !is_skb_data(right))
 243                 return 0;
 244
 245         tag_as_user_data(expr->left);
 246         return 1;
 247 }
 248
 249 static int handle_get_user(struct expression *expr)
 250 {
 251         char *name;
 252         int ret = 0;
 253
 254         name = get_macro_name(expr->pos);
 255         if (!name || strcmp(name, "get_user") != 0)
 256                 return 0;
 257
 258         name = expr_to_var(expr->right);
 259         if (!name || strcmp(name, "__val_gu") != 0)
 260                 goto free;
 261         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 262         ret = 1;
 263 free:
 264         free_string(name);
 265         return ret;
 266 }
 267
 268 static void match_assign(struct expression *expr)
 269 {
 270         struct range_list *rl;
 271
 272         if (is_fake_call(expr->right))
 273                 return;
 274         if (handle_struct_assignment(expr))
 275                 return;
 276         if (handle_get_user(expr))
 277                 return;
 278
 279         if (expr->right->type == EXPR_CALL ||
 280             !get_user_rl(expr->right, &rl))
 281                 goto clear_old_state;
 282
 283         rl = cast_rl(get_type(expr->left), rl);
 284         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 285
 286         return;
 287
 288 clear_old_state:
 289         if (get_state_expr(my_id, expr->left))
 290                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 291 }
 292
 293 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 294 {
 295         tag_as_user_data(expr->left);
 296 }
 297
 298 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 299 {
 300         char *macro;
 301
 302         if (!expr)
 303                 return 0;
 304         macro = get_macro_name(expr->pos);
 305
 306         if (!macro)
 307                 return 0;
 308
 309         if (strcmp(macro, "ntohl") == 0) {
 310                 *rl = alloc_whole_rl(&uint_ctype);
 311                 return 1;
 312         }
 313         if (strcmp(macro, "ntohs") == 0) {
 314                 *rl = alloc_whole_rl(&ushort_ctype);
 315                 return 1;
 316         }
 317         return 0;
 318 }
 319
 320 static int user_data_flag;
 321 static struct range_list *var_user_rl(struct expression *expr)
 322 {
 323         struct smatch_state *state;
 324         struct range_list *rl;
 325         struct range_list *absolute_rl;
 326
 327         if (get_user_macro_rl(expr, &rl))
 328                 goto found;
 329
 330         if (comes_from_skb_data(expr)) {
 331                 rl = alloc_whole_rl(get_type(expr));
 332                 goto found;
 333         }
 334
 335         state = get_state_expr(my_id, expr);
 336         if (state && estate_rl(state)) {
 337                 rl = estate_rl(state);
 338                 goto found;
 339         }
 340
 341         return NULL;
 342 found:
 343         user_data_flag = 1;
 344         absolute_rl = var_to_absolute_rl(expr);
 345         return clone_rl(rl_intersection(rl, absolute_rl));
 346 }
 347
 348 int get_user_rl(struct expression *expr, struct range_list **rl)
 349 {
 350
 351         user_data_flag = 0;
 352         custom_get_absolute_rl(expr, &var_user_rl, rl);
 353         if (!user_data_flag) {
 354                 *rl = NULL;
 355                 return 0;
 356         }
 357         return 1;
 358 }
 359
 360 static void match_call_info(struct expression *expr)
 361 {
 362         struct range_list *rl;
 363         struct expression *arg;
 364         int i = 0;
 365
 366         i = -1;
 367         FOR_EACH_PTR(expr->args, arg) {
 368                 i++;
 369
 370                 if (!get_user_rl(arg, &rl))
 371                         continue;
 372
 373                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 374         } END_FOR_EACH_PTR(arg);
 375 }
 376
 377 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 378 {
 379         struct smatch_state *state;
 380         struct range_list *rl;
 381
 382         if (strcmp(sm->state->name, "") == 0)
 383                 return;
 384
 385         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 386         if (!state || !estate_rl(state))
 387                 rl = estate_rl(sm->state);
 388         else
 389                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 390
 391         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 392 }
 393
 394 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 395 {
 396         struct range_list *rl = NULL;
 397         struct smatch_state *state;
 398         struct symbol *type;
 399         char fullname[256];
 400
 401         if (strcmp(key, "*$") == 0)
 402                 snprintf(fullname, sizeof(fullname), "*%s", name);
 403         else if (strncmp(key, "$", 1) == 0)
 404                 snprintf(fullname, 256, "%s%s", name, key + 1);
 405         else
 406                 return;
 407
 408         type = get_member_type_from_key(symbol_expression(sym), key);
 409
 410         /* if the caller passes a void pointer with user data */
 411         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 412                 struct expression *expr = symbol_expression(sym);
 413
 414                 tag_as_user_data(expr);
 415                 return;
 416         }
 417         str_to_rl(type, value, &rl);
 418         state = alloc_estate_rl(rl);
 419         set_state(my_id, fullname, sym, state);
 420 }
 421
 422 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 423 {
 424         set_state(my_call_id, "this_function", NULL, &called);
 425 }
 426
 427 static void match_syscall_definition(struct symbol *sym)
 428 {
 429         struct symbol *arg;
 430         char *macro;
 431         char *name;
 432         int is_syscall = 0;
 433
 434         macro = get_macro_name(sym->pos);
 435         if (macro &&
 436             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 437              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 438                 is_syscall = 1;
 439
 440         name = get_function();
 441         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 442                 if (name && strncmp(name, "sys_", 4) == 0)
 443                         is_syscall = 1;
 444         }
 445
 446         if (name && strncmp(name, "compat_sys_", 11) == 0)
 447                 is_syscall = 1;
 448
 449         if (!is_syscall)
 450                 return;
 451
 452         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 453                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 454         } END_FOR_EACH_PTR(arg);
 455 }
 456
 457 void check_user_data2(int id)
 458 {
 459         my_id = id;
 460
 461         if (option_project != PROJ_KERNEL)
 462                 return;
 463
 464         add_unmatched_state_hook(my_id, &empty_state);
 465         add_merge_hook(my_id, &merge_estates);
 466
 467         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 468         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 469         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 470         add_function_hook("_kstrtoull", &match_user_copy, INT_PTR(2));
 471
 472         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 473         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 474
 475         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 476
 477         add_hook(&match_assign, ASSIGNMENT_HOOK);
 478
 479         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 480         add_member_info_callback(my_id, struct_member_callback);
 481         select_caller_info_hook(set_param_user_data, USER_DATA3);
 482 }
 483
 484 void check_user_data3(int id)
 485 {
 486         my_call_id = id;
 487
 488         if (option_project != PROJ_KERNEL)
 489                 return;
 490         select_caller_info_hook(set_called, INTERNAL);
 491 }
 492