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 void match_sscanf(const char *fn, struct expression *expr, void *unused)
 146 {
 147         struct expression *arg;
 148         int i;
 149
 150         i = -1;
 151         FOR_EACH_PTR(expr->args, arg) {
 152                 i++;
 153                 if (i < 2)
 154                         continue;
 155                 tag_as_user_data(arg);
 156         } END_FOR_EACH_PTR(arg);
 157 }
 158
 159 static int points_to_user_data(struct expression *expr)
 160 {
 161         struct smatch_state *state;
 162         char buf[256];
 163         struct symbol *sym;
 164         char *name;
 165         int ret = 0;
 166
 167         name = expr_to_var_sym(expr, &sym);
 168         if (!name || !sym)
 169                 goto free;
 170         snprintf(buf, sizeof(buf), "*%s", name);
 171         state = get_state(my_id, buf, sym);
 172         if (state && estate_rl(state))
 173                 ret = 1;
 174 free:
 175         free_string(name);
 176         return ret;
 177 }
 178
 179 static int is_skb_data(struct expression *expr)
 180 {
 181         struct symbol *sym;
 182
 183         expr = strip_expr(expr);
 184         if (!expr || expr->type != EXPR_DEREF)
 185                 return 0;
 186
 187         if (!expr->member)
 188                 return 0;
 189         if (strcmp(expr->member->name, "data") != 0)
 190                 return 0;
 191
 192         sym = expr_to_sym(expr->deref);
 193         if (!sym)
 194                 return 0;
 195         sym = get_real_base_type(sym);
 196         if (!sym || sym->type != SYM_PTR)
 197                 return 0;
 198         sym = get_real_base_type(sym);
 199         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 200                 return 0;
 201         if (strcmp(sym->ident->name, "sk_buff") != 0)
 202                 return 0;
 203
 204         return 1;
 205 }
 206
 207 static int comes_from_skb_data(struct expression *expr)
 208 {
 209         expr = strip_expr(expr);
 210         if (!expr)
 211                 return 0;
 212
 213         switch (expr->type) {
 214         case EXPR_BINOP:
 215                 if (comes_from_skb_data(expr->left))
 216                         return 1;
 217                 if (comes_from_skb_data(expr->right))
 218                         return 1;
 219                 return 0;
 220         case EXPR_PREOP:
 221                 return comes_from_skb_data(expr->unop);
 222         case EXPR_DEREF:
 223                 if (is_skb_data(expr))
 224                         return 1;
 225                 return comes_from_skb_data(expr->deref);
 226         default:
 227                 return 0;
 228         }
 229 }
 230
 231
 232 static int handle_struct_assignment(struct expression *expr)
 233 {
 234         struct expression *right;
 235         struct symbol *type;
 236
 237         type = get_type(expr->left);
 238         if (!type || type->type != SYM_PTR)
 239                 return 0;
 240         type = get_real_base_type(type);
 241         if (!type || type->type != SYM_STRUCT)
 242                 return 0;
 243
 244         /*
 245          * Ignore struct to struct assignments because for those we look at the
 246          * individual members.
 247          */
 248         right = strip_expr(expr->right);
 249         type = get_type(right);
 250         if (!type || type->type != SYM_PTR)
 251                 return 0;
 252         type = get_real_base_type(type);
 253         if (type && type->type == SYM_STRUCT)
 254                 return 0;
 255
 256         if (!points_to_user_data(right) && !is_skb_data(right))
 257                 return 0;
 258
 259         tag_as_user_data(expr->left);
 260         return 1;
 261 }
 262
 263 static int handle_get_user(struct expression *expr)
 264 {
 265         char *name;
 266         int ret = 0;
 267
 268         name = get_macro_name(expr->pos);
 269         if (!name || strcmp(name, "get_user") != 0)
 270                 return 0;
 271
 272         name = expr_to_var(expr->right);
 273         if (!name || strcmp(name, "__val_gu") != 0)
 274                 goto free;
 275         set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 276         ret = 1;
 277 free:
 278         free_string(name);
 279         return ret;
 280 }
 281
 282 static void match_assign(struct expression *expr)
 283 {
 284         struct range_list *rl;
 285
 286         if (is_fake_call(expr->right))
 287                 return;
 288         if (handle_struct_assignment(expr))
 289                 return;
 290         if (handle_get_user(expr))
 291                 return;
 292
 293         if (expr->right->type == EXPR_CALL ||
 294             !get_user_rl(expr->right, &rl))
 295                 goto clear_old_state;
 296
 297         rl = cast_rl(get_type(expr->left), rl);
 298         set_state_expr(my_id, expr->left, alloc_estate_rl(rl));
 299
 300         return;
 301
 302 clear_old_state:
 303         if (get_state_expr(my_id, expr->left))
 304                 set_state_expr(my_id, expr->left, alloc_estate_empty());
 305 }
 306
 307 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 308 {
 309         tag_as_user_data(expr->left);
 310 }
 311
 312 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
 313 {
 314         char *macro;
 315
 316         if (!expr)
 317                 return 0;
 318         macro = get_macro_name(expr->pos);
 319
 320         if (!macro)
 321                 return 0;
 322
 323         if (strcmp(macro, "ntohl") == 0) {
 324                 *rl = alloc_whole_rl(&uint_ctype);
 325                 return 1;
 326         }
 327         if (strcmp(macro, "ntohs") == 0) {
 328                 *rl = alloc_whole_rl(&ushort_ctype);
 329                 return 1;
 330         }
 331         return 0;
 332 }
 333
 334 static int user_data_flag;
 335 static struct range_list *var_user_rl(struct expression *expr)
 336 {
 337         struct smatch_state *state;
 338         struct range_list *rl;
 339         struct range_list *absolute_rl;
 340
 341         if (get_user_macro_rl(expr, &rl))
 342                 goto found;
 343
 344         if (comes_from_skb_data(expr)) {
 345                 rl = alloc_whole_rl(get_type(expr));
 346                 goto found;
 347         }
 348
 349         state = get_state_expr(my_id, expr);
 350         if (state && estate_rl(state)) {
 351                 rl = estate_rl(state);
 352                 goto found;
 353         }
 354
 355         return NULL;
 356 found:
 357         user_data_flag = 1;
 358         absolute_rl = var_to_absolute_rl(expr);
 359         return clone_rl(rl_intersection(rl, absolute_rl));
 360 }
 361
 362 int get_user_rl(struct expression *expr, struct range_list **rl)
 363 {
 364
 365         user_data_flag = 0;
 366         custom_get_absolute_rl(expr, &var_user_rl, rl);
 367         if (!user_data_flag) {
 368                 *rl = NULL;
 369                 return 0;
 370         }
 371         return 1;
 372 }
 373
 374 static void match_call_info(struct expression *expr)
 375 {
 376         struct range_list *rl;
 377         struct expression *arg;
 378         int i = 0;
 379
 380         i = -1;
 381         FOR_EACH_PTR(expr->args, arg) {
 382                 i++;
 383
 384                 if (!get_user_rl(arg, &rl))
 385                         continue;
 386
 387                 sql_insert_caller_info(expr, USER_DATA3, i, "$", show_rl(rl));
 388         } END_FOR_EACH_PTR(arg);
 389 }
 390
 391 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 392 {
 393         struct smatch_state *state;
 394         struct range_list *rl;
 395
 396         if (strcmp(sm->state->name, "") == 0)
 397                 return;
 398
 399         state = get_state(SMATCH_EXTRA, sm->name, sm->sym);
 400         if (!state || !estate_rl(state))
 401                 rl = estate_rl(sm->state);
 402         else
 403                 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
 404
 405         sql_insert_caller_info(call, USER_DATA3, param, printed_name, show_rl(rl));
 406 }
 407
 408 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 409 {
 410         struct range_list *rl = NULL;
 411         struct smatch_state *state;
 412         struct symbol *type;
 413         char fullname[256];
 414
 415         if (strcmp(key, "*$") == 0)
 416                 snprintf(fullname, sizeof(fullname), "*%s", name);
 417         else if (strncmp(key, "$", 1) == 0)
 418                 snprintf(fullname, 256, "%s%s", name, key + 1);
 419         else
 420                 return;
 421
 422         type = get_member_type_from_key(symbol_expression(sym), key);
 423
 424         /* if the caller passes a void pointer with user data */
 425         if (strcmp(key, "*$") == 0 && type && type != &void_ctype) {
 426                 struct expression *expr = symbol_expression(sym);
 427
 428                 tag_as_user_data(expr);
 429                 return;
 430         }
 431         str_to_rl(type, value, &rl);
 432         state = alloc_estate_rl(rl);
 433         set_state(my_id, fullname, sym, state);
 434 }
 435
 436 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
 437 {
 438         set_state(my_call_id, "this_function", NULL, &called);
 439 }
 440
 441 static void match_syscall_definition(struct symbol *sym)
 442 {
 443         struct symbol *arg;
 444         char *macro;
 445         char *name;
 446         int is_syscall = 0;
 447
 448         macro = get_macro_name(sym->pos);
 449         if (macro &&
 450             (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
 451              strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
 452                 is_syscall = 1;
 453
 454         name = get_function();
 455         if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
 456                 if (name && strncmp(name, "sys_", 4) == 0)
 457                         is_syscall = 1;
 458         }
 459
 460         if (name && strncmp(name, "compat_sys_", 11) == 0)
 461                 is_syscall = 1;
 462
 463         if (!is_syscall)
 464                 return;
 465
 466         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 467                 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
 468         } END_FOR_EACH_PTR(arg);
 469 }
 470
 471 void check_user_data2(int id)
 472 {
 473         my_id = id;
 474
 475         if (option_project != PROJ_KERNEL)
 476                 return;
 477
 478         add_unmatched_state_hook(my_id, &empty_state);
 479         add_merge_hook(my_id, &merge_estates);
 480
 481         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 482         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 483         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 484         add_function_hook("_kstrtoull", &match_user_copy, INT_PTR(2));
 485
 486         add_function_hook("sscanf", &match_sscanf, NULL);
 487
 488         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 489         add_function_assign_hook("kmap_atomic", &match_user_assign_function, NULL);
 490
 491         add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
 492
 493         add_hook(&match_assign, ASSIGNMENT_HOOK);
 494
 495         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 496         add_member_info_callback(my_id, struct_member_callback);
 497         select_caller_info_hook(set_param_user_data, USER_DATA3);
 498 }
 499
 500 void check_user_data3(int id)
 501 {
 502         my_call_id = id;
 503
 504         if (option_project != PROJ_KERNEL)
 505                 return;
 506         select_caller_info_hook(set_called, INTERNAL);
 507 }
 508