check_rosenberg.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 /* Does a search for Dan Rosenberg style info leaks */
  19
  20 /* fixme: struct includes a struct with a hole in it */
  21 /* function is called that clears the struct */
  22
  23 #include "scope.h"
  24 #include "smatch.h"
  25 #include "smatch_function_hashtable.h"
  26 #include "smatch_slist.h"
  27 #include "smatch_extra.h"
  28
  29 static int my_whole_id;
  30 static int my_member_id;
  31 static int skb_put_id;
  32
  33 STATE(cleared);
  34
  35 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
  36 {
  37         struct symbol *type;
  38
  39         type = get_real_base_type(sym);
  40         if (!type || type->type != SYM_STRUCT)
  41                 return;
  42
  43         if (!cur_func_sym)
  44                 return;
  45
  46         if (name && strstr(name, "->"))
  47                 return;
  48
  49         set_state(my_member_id, name, sym, state);
  50 }
  51
  52 static void print_holey_warning(struct expression *data, const char *member)
  53 {
  54         char *name;
  55
  56         name = expr_to_str(data);
  57         if (member) {
  58                 sm_warning("check that '%s' doesn't leak information (struct has a hole after '%s')",
  59                        name, member);
  60         } else {
  61                 sm_warning("check that '%s' doesn't leak information (struct has holes)",
  62                        name);
  63         }
  64         free_string(name);
  65 }
  66
  67 static int check_struct(struct expression *expr, struct symbol *type)
  68 {
  69         struct symbol *base_type, *prev_type;
  70         struct symbol *tmp, *prev;
  71         int align;
  72
  73         if (type->ctype.alignment == 1)
  74                 return 0;
  75
  76         align = 0;
  77         prev = NULL;
  78         prev_type = NULL;
  79         FOR_EACH_PTR(type->symbol_list, tmp) {
  80                 base_type = get_real_base_type(tmp);
  81                 if (base_type && base_type->type == SYM_STRUCT) {
  82                         if (check_struct(expr, base_type))
  83                                 return 1;
  84                 }
  85                 if (base_type && base_type->type == SYM_BITFIELD &&
  86                     prev_type && prev_type->type == SYM_BITFIELD)
  87                         goto next;
  88
  89                 if (!tmp->ctype.alignment) {
  90                         sm_perror("cannot determine the alignment here");
  91                 } else if (align % tmp->ctype.alignment) {
  92
  93                         print_holey_warning(expr, prev->ident ? prev->ident->name : "<unknown>");
  94                         return 1;
  95                 }
  96
  97 next:
  98                 if (base_type == &bool_ctype)
  99                         align += 1;
 100                 else if (type_bits(tmp) <= 0)
 101                         align = 0;
 102                 else
 103                         align += type_bytes(tmp);
 104
 105                 prev = tmp;
 106                 prev_type = base_type;
 107         } END_FOR_EACH_PTR(tmp);
 108
 109         // FIXME: this isn't the correct fix.  See sbni_siocdevprivate().
 110         if (prev_type && prev_type->type == SYM_BITFIELD)
 111                 return 0;
 112         if (align % type->ctype.alignment) {
 113                         sm_msg("%s: tmp='%s' align=%d ctype.align=%ld type='%s'", __func__,
 114                                tmp->ident ? tmp->ident->name : "<unknown>",
 115                                align, tmp->ctype.alignment,
 116                                type_to_str(get_real_base_type(tmp)));
 117
 118                 print_holey_warning(expr, (prev && prev->ident) ? prev->ident->name : "<unknown>");
 119                 return 1;
 120         }
 121
 122         return 0;
 123 }
 124
 125 static int warn_on_holey_struct(struct expression *expr)
 126 {
 127         struct symbol *type;
 128         type = get_type(expr);
 129         if (!type || type->type != SYM_STRUCT)
 130                 return 0;
 131
 132         return check_struct(expr, type);
 133 }
 134
 135 static int has_global_scope(struct expression *expr)
 136 {
 137         struct symbol *sym;
 138
 139         if (expr->type != EXPR_SYMBOL)
 140                 return FALSE;
 141         sym = expr->symbol;
 142         if (!sym)
 143                 return FALSE;
 144         return toplevel(sym->scope);
 145 }
 146
 147 static int was_initialized(struct expression *expr)
 148 {
 149         struct symbol *sym, *type;
 150         char *name;
 151
 152         name = expr_to_var_sym(expr, &sym);
 153         if (!name)
 154                 return 0;
 155         if (!sym->initializer)
 156                 return 0;
 157         type = get_real_base_type(sym);
 158         if (!type)
 159                 return 0;
 160         if (type->type != SYM_STRUCT)
 161                 return 1;
 162
 163         /* Fully initializing a struct does not clear the holes */
 164         if (ptr_list_size((struct ptr_list *)sym->initializer->expr_list) >=
 165             ptr_list_size((struct ptr_list *)type->symbol_list))
 166                 return 0;
 167
 168         return 1;
 169 }
 170
 171 static void match_clear(const char *fn, struct expression *expr, void *_arg_no)
 172 {
 173         struct expression *ptr, *tmp;
 174         int arg_no = PTR_INT(_arg_no);
 175
 176         ptr = get_argument_from_call_expr(expr->args, arg_no);
 177         if (!ptr)
 178                 return;
 179         tmp = get_assigned_expr(ptr);
 180         if (tmp)
 181                 ptr = tmp;
 182         ptr = strip_expr(ptr);
 183         if (ptr->type != EXPR_PREOP || ptr->op != '&')
 184                 return;
 185         ptr = strip_expr(ptr->unop);
 186         set_state_expr(my_whole_id, ptr, &cleared);
 187 }
 188
 189 static int was_memset(struct expression *expr)
 190 {
 191         if (get_state_expr(my_whole_id, expr) == &cleared)
 192                 return 1;
 193         return 0;
 194 }
 195
 196 static int member_initialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
 197 {
 198         char buf[256];
 199         struct symbol *base;
 200
 201         base = get_base_type(member);
 202         if (!base || base->type != SYM_BASETYPE || !member->ident)
 203                 return FALSE;
 204
 205         if (pointer)
 206                 snprintf(buf, 256, "%s->%s", name, member->ident->name);
 207         else
 208                 snprintf(buf, 256, "%s.%s", name, member->ident->name);
 209
 210         if (get_state(my_member_id, buf, outer))
 211                 return TRUE;
 212
 213         return FALSE;
 214 }
 215
 216 static int member_uninitialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
 217 {
 218         char buf[256];
 219         struct symbol *base;
 220         struct sm_state *sm;
 221
 222         base = get_base_type(member);
 223         if (!base || base->type != SYM_BASETYPE || !member->ident)
 224                 return FALSE;
 225
 226         if (pointer)
 227                 snprintf(buf, 256, "%s->%s", name, member->ident->name);
 228         else
 229                 snprintf(buf, 256, "%s.%s", name, member->ident->name);
 230
 231         sm = get_sm_state(my_member_id, buf, outer);
 232         if (sm && !slist_has_state(sm->possible, &undefined))
 233                 return FALSE;
 234
 235         sm_warning("check that '%s' doesn't leak information", buf);
 236         return TRUE;
 237 }
 238
 239 static int check_members_initialized(struct expression *expr)
 240 {
 241         char *name;
 242         struct symbol *outer;
 243         struct symbol *sym;
 244         struct symbol *tmp;
 245         int pointer = 0;
 246         int printed = 0;
 247
 248         sym = get_type(expr);
 249         if (sym && sym->type == SYM_PTR) {
 250                 pointer = 1;
 251                 sym = get_real_base_type(sym);
 252         }
 253         if (!sym)
 254                 return 0;
 255         if (sym->type != SYM_STRUCT)
 256                 return 0;
 257
 258         name = expr_to_var_sym(expr, &outer);
 259
 260         /*
 261          * check that at least one member was set.  If all of them were not set
 262          * it's more likely a problem in the check than a problem in the kernel
 263          * code.
 264          */
 265         FOR_EACH_PTR(sym->symbol_list, tmp) {
 266                 if (member_initialized(name, outer, tmp, pointer))
 267                         goto check;
 268         } END_FOR_EACH_PTR(tmp);
 269         goto out;
 270
 271 check:
 272         FOR_EACH_PTR(sym->symbol_list, tmp) {
 273                 if (member_uninitialized(name, outer, tmp, pointer)) {
 274                         printed = 1;
 275                         goto out;
 276                 }
 277         } END_FOR_EACH_PTR(tmp);
 278 out:
 279         free_string(name);
 280         return printed;
 281 }
 282
 283 static void check_was_initialized(struct expression *data)
 284 {
 285         data = strip_expr(data);
 286         if (!data)
 287                 return;
 288         if (data->type == EXPR_PREOP && data->op == '&')
 289                 data = strip_expr(data->unop);
 290         if (data->type != EXPR_SYMBOL)
 291                 return;
 292
 293         if (has_global_scope(data))
 294                 return;
 295         if (was_initialized(data))
 296                 return;
 297         if (was_memset(data))
 298                 return;
 299         if (warn_on_holey_struct(data))
 300                 return;
 301         check_members_initialized(data);
 302 }
 303
 304 static void check_skb_put(struct expression *data)
 305 {
 306         data = strip_expr(data);
 307         if (!data)
 308                 return;
 309         if (data->type == EXPR_PREOP && data->op == '&')
 310                 data = strip_expr(data->unop);
 311
 312         if (was_memset(data))
 313                 return;
 314         if (warn_on_holey_struct(data))
 315                 return;
 316         check_members_initialized(data);
 317 }
 318
 319 static void match_copy_to_user(const char *fn, struct expression *expr, void *_arg)
 320 {
 321         int arg = PTR_INT(_arg);
 322         struct expression *data;
 323
 324         data = get_argument_from_call_expr(expr->args, arg);
 325         data = strip_expr(data);
 326         if (!data)
 327                 return;
 328         if (data->type != EXPR_PREOP || data->op != '&')
 329                 return;
 330         check_was_initialized(data);
 331 }
 332
 333 static void db_param_cleared(struct expression *expr, int param, char *key, char *value)
 334 {
 335         while (expr->type == EXPR_ASSIGNMENT)
 336                 expr = strip_expr(expr->right);
 337         if (expr->type != EXPR_CALL)
 338                 return;
 339
 340         match_clear(NULL, expr, INT_PTR(param));
 341 }
 342
 343 static struct smatch_state *alloc_expr_state(struct expression *expr)
 344 {
 345         struct smatch_state *state;
 346         char *name;
 347
 348         name = expr_to_str(expr);
 349         if (!name)
 350                 return NULL;
 351
 352         state = __alloc_smatch_state(0);
 353         expr = strip_expr(expr);
 354         state->name = alloc_sname(name);
 355         free_string(name);
 356         state->data = expr;
 357         return state;
 358 }
 359
 360 static void match_skb_put(const char *fn, struct expression *expr, void *unused)
 361 {
 362         struct symbol *type;
 363         struct smatch_state *state;
 364
 365         type = get_type(expr->left);
 366         type = get_real_base_type(type);
 367         if (!type || type->type != SYM_STRUCT)
 368                 return;
 369         state = alloc_expr_state(expr->left);
 370         set_state_expr(skb_put_id, expr->left, state);
 371 }
 372
 373 static void match_return_skb_put(struct expression *expr)
 374 {
 375         struct sm_state *sm;
 376         struct stree *stree;
 377
 378         if (is_error_return(expr))
 379                 return;
 380
 381         stree = __get_cur_stree();
 382
 383         FOR_EACH_MY_SM(skb_put_id, stree, sm) {
 384                 check_skb_put(sm->state->data);
 385         } END_FOR_EACH_SM(sm);
 386 }
 387
 388 static void register_clears_argument(void)
 389 {
 390         struct token *token;
 391         const char *func;
 392         int arg;
 393
 394         token = get_tokens_file("kernel.clears_argument");
 395         if (!token)
 396                 return;
 397         if (token_type(token) != TOKEN_STREAMBEGIN)
 398                 return;
 399         token = token->next;
 400         while (token_type(token) != TOKEN_STREAMEND) {
 401                 if (token_type(token) != TOKEN_IDENT)
 402                         return;
 403                 func = show_ident(token->ident);
 404                 token = token->next;
 405                 if (token_type(token) != TOKEN_NUMBER)
 406                         return;
 407                 arg = atoi(token->number);
 408
 409                 add_function_hook(func, &match_clear, INT_PTR(arg));
 410                 token = token->next;
 411         }
 412         clear_token_alloc();
 413 }
 414
 415 static void register_copy_funcs_from_file(void)
 416 {
 417         struct token *token;
 418         const char *func;
 419         int arg;
 420
 421         token = get_tokens_file("kernel.rosenberg_funcs");
 422         if (!token)
 423                 return;
 424         if (token_type(token) != TOKEN_STREAMBEGIN)
 425                 return;
 426         token = token->next;
 427         while (token_type(token) != TOKEN_STREAMEND) {
 428                 if (token_type(token) != TOKEN_IDENT)
 429                         return;
 430                 func = show_ident(token->ident);
 431                 token = token->next;
 432                 if (token_type(token) != TOKEN_NUMBER)
 433                         return;
 434                 arg = atoi(token->number);
 435                 add_function_hook(func, &match_copy_to_user, INT_PTR(arg));
 436                 token = token->next;
 437         }
 438         clear_token_alloc();
 439 }
 440
 441 void check_rosenberg(int id)
 442 {
 443         if (option_project != PROJ_KERNEL)
 444                 return;
 445         my_whole_id = id;
 446
 447         add_function_hook("memset", &match_clear, INT_PTR(0));
 448         add_function_hook("memcpy", &match_clear, INT_PTR(0));
 449         add_function_hook("memzero", &match_clear, INT_PTR(0));
 450         add_function_hook("__memset", &match_clear, INT_PTR(0));
 451         add_function_hook("__memcpy", &match_clear, INT_PTR(0));
 452         add_function_hook("__memzero", &match_clear, INT_PTR(0));
 453         add_function_hook("__builtin_memset", &match_clear, INT_PTR(0));
 454         add_function_hook("__builtin_memcpy", &match_clear, INT_PTR(0));
 455
 456         register_clears_argument();
 457         select_return_states_hook(BUF_CLEARED, &db_param_cleared);
 458
 459         register_copy_funcs_from_file();
 460 }
 461
 462 void check_rosenberg2(int id)
 463 {
 464         if (option_project != PROJ_KERNEL)
 465                 return;
 466
 467         my_member_id = id;
 468         set_dynamic_states(my_member_id);
 469         add_extra_mod_hook(&extra_mod_hook);
 470 }
 471
 472 void check_rosenberg3(int id)
 473 {
 474         if (option_project != PROJ_KERNEL)
 475                 return;
 476
 477         skb_put_id = id;
 478         set_dynamic_states(skb_put_id);
 479         add_function_assign_hook("skb_put", &match_skb_put, NULL);
 480         add_hook(&match_return_skb_put, RETURN_HOOK);
 481 }
 482