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 void match_clear(const char *fn, struct expression *expr, void *_arg_no)
 148 {
 149         struct expression *ptr, *tmp;
 150         int arg_no = PTR_INT(_arg_no);
 151
 152         ptr = get_argument_from_call_expr(expr->args, arg_no);
 153         if (!ptr)
 154                 return;
 155         tmp = get_assigned_expr(ptr);
 156         if (tmp)
 157                 ptr = tmp;
 158         ptr = strip_expr(ptr);
 159         if (ptr->type != EXPR_PREOP || ptr->op != '&')
 160                 return;
 161         ptr = strip_expr(ptr->unop);
 162         set_state_expr(my_whole_id, ptr, &cleared);
 163 }
 164
 165 static int was_memset(struct expression *expr)
 166 {
 167         if (get_state_expr(my_whole_id, expr) == &cleared)
 168                 return 1;
 169         return 0;
 170 }
 171
 172 static int member_initialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
 173 {
 174         char buf[256];
 175         struct symbol *base;
 176
 177         base = get_base_type(member);
 178         if (!base || base->type != SYM_BASETYPE || !member->ident)
 179                 return FALSE;
 180
 181         if (pointer)
 182                 snprintf(buf, 256, "%s->%s", name, member->ident->name);
 183         else
 184                 snprintf(buf, 256, "%s.%s", name, member->ident->name);
 185
 186         if (get_state(my_member_id, buf, outer))
 187                 return TRUE;
 188
 189         return FALSE;
 190 }
 191
 192 static int member_uninitialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
 193 {
 194         char buf[256];
 195         struct symbol *base;
 196         struct sm_state *sm;
 197
 198         base = get_base_type(member);
 199         if (!base || base->type != SYM_BASETYPE || !member->ident)
 200                 return FALSE;
 201
 202         if (pointer)
 203                 snprintf(buf, 256, "%s->%s", name, member->ident->name);
 204         else
 205                 snprintf(buf, 256, "%s.%s", name, member->ident->name);
 206
 207         sm = get_sm_state(my_member_id, buf, outer);
 208         if (sm && !slist_has_state(sm->possible, &undefined))
 209                 return FALSE;
 210
 211         sm_warning("check that '%s' doesn't leak information", buf);
 212         return TRUE;
 213 }
 214
 215 static int check_members_initialized(struct expression *expr)
 216 {
 217         char *name;
 218         struct symbol *outer;
 219         struct symbol *sym;
 220         struct symbol *tmp;
 221         int pointer = 0;
 222         int printed = 0;
 223
 224         sym = get_type(expr);
 225         if (sym && sym->type == SYM_PTR) {
 226                 pointer = 1;
 227                 sym = get_real_base_type(sym);
 228         }
 229         if (!sym)
 230                 return 0;
 231         if (sym->type != SYM_STRUCT)
 232                 return 0;
 233
 234         name = expr_to_var_sym(expr, &outer);
 235
 236         /*
 237          * check that at least one member was set.  If all of them were not set
 238          * it's more likely a problem in the check than a problem in the kernel
 239          * code.
 240          */
 241         FOR_EACH_PTR(sym->symbol_list, tmp) {
 242                 if (member_initialized(name, outer, tmp, pointer))
 243                         goto check;
 244         } END_FOR_EACH_PTR(tmp);
 245         goto out;
 246
 247 check:
 248         FOR_EACH_PTR(sym->symbol_list, tmp) {
 249                 if (member_uninitialized(name, outer, tmp, pointer)) {
 250                         printed = 1;
 251                         goto out;
 252                 }
 253         } END_FOR_EACH_PTR(tmp);
 254 out:
 255         free_string(name);
 256         return printed;
 257 }
 258
 259 static void check_was_initialized(struct expression *data)
 260 {
 261         data = strip_expr(data);
 262         if (!data)
 263                 return;
 264         if (data->type == EXPR_PREOP && data->op == '&')
 265                 data = strip_expr(data->unop);
 266         if (data->type != EXPR_SYMBOL)
 267                 return;
 268
 269         if (has_global_scope(data))
 270                 return;
 271         if (was_memset(data))
 272                 return;
 273         if (warn_on_holey_struct(data))
 274                 return;
 275         check_members_initialized(data);
 276 }
 277
 278 static void check_skb_put(struct expression *data)
 279 {
 280         data = strip_expr(data);
 281         if (!data)
 282                 return;
 283         if (data->type == EXPR_PREOP && data->op == '&')
 284                 data = strip_expr(data->unop);
 285
 286         if (was_memset(data))
 287                 return;
 288         if (warn_on_holey_struct(data))
 289                 return;
 290         check_members_initialized(data);
 291 }
 292
 293 static void match_copy_to_user(const char *fn, struct expression *expr, void *_arg)
 294 {
 295         int arg = PTR_INT(_arg);
 296         struct expression *data;
 297
 298         data = get_argument_from_call_expr(expr->args, arg);
 299         data = strip_expr(data);
 300         if (!data)
 301                 return;
 302         if (data->type != EXPR_PREOP || data->op != '&')
 303                 return;
 304         check_was_initialized(data);
 305 }
 306
 307 static void db_param_cleared(struct expression *expr, int param, char *key, char *value)
 308 {
 309         while (expr->type == EXPR_ASSIGNMENT)
 310                 expr = strip_expr(expr->right);
 311         if (expr->type != EXPR_CALL)
 312                 return;
 313
 314         match_clear(NULL, expr, INT_PTR(param));
 315 }
 316
 317 static struct smatch_state *alloc_expr_state(struct expression *expr)
 318 {
 319         struct smatch_state *state;
 320         char *name;
 321
 322         name = expr_to_str(expr);
 323         if (!name)
 324                 return NULL;
 325
 326         state = __alloc_smatch_state(0);
 327         expr = strip_expr(expr);
 328         state->name = alloc_sname(name);
 329         free_string(name);
 330         state->data = expr;
 331         return state;
 332 }
 333
 334 static void match_skb_put(const char *fn, struct expression *expr, void *unused)
 335 {
 336         struct symbol *type;
 337         struct smatch_state *state;
 338
 339         type = get_type(expr->left);
 340         type = get_real_base_type(type);
 341         if (!type || type->type != SYM_STRUCT)
 342                 return;
 343         state = alloc_expr_state(expr->left);
 344         set_state_expr(skb_put_id, expr->left, state);
 345 }
 346
 347 static void match_return_skb_put(struct expression *expr)
 348 {
 349         struct sm_state *sm;
 350         struct stree *stree;
 351
 352         if (is_error_return(expr))
 353                 return;
 354
 355         stree = __get_cur_stree();
 356
 357         FOR_EACH_MY_SM(skb_put_id, stree, sm) {
 358                 check_skb_put(sm->state->data);
 359         } END_FOR_EACH_SM(sm);
 360 }
 361
 362 static void register_clears_argument(void)
 363 {
 364         struct token *token;
 365         const char *func;
 366         int arg;
 367
 368         token = get_tokens_file("kernel.clears_argument");
 369         if (!token)
 370                 return;
 371         if (token_type(token) != TOKEN_STREAMBEGIN)
 372                 return;
 373         token = token->next;
 374         while (token_type(token) != TOKEN_STREAMEND) {
 375                 if (token_type(token) != TOKEN_IDENT)
 376                         return;
 377                 func = show_ident(token->ident);
 378                 token = token->next;
 379                 if (token_type(token) != TOKEN_NUMBER)
 380                         return;
 381                 arg = atoi(token->number);
 382
 383                 add_function_hook(func, &match_clear, INT_PTR(arg));
 384                 token = token->next;
 385         }
 386         clear_token_alloc();
 387 }
 388
 389 static void register_copy_funcs_from_file(void)
 390 {
 391         struct token *token;
 392         const char *func;
 393         int arg;
 394
 395         token = get_tokens_file("kernel.rosenberg_funcs");
 396         if (!token)
 397                 return;
 398         if (token_type(token) != TOKEN_STREAMBEGIN)
 399                 return;
 400         token = token->next;
 401         while (token_type(token) != TOKEN_STREAMEND) {
 402                 if (token_type(token) != TOKEN_IDENT)
 403                         return;
 404                 func = show_ident(token->ident);
 405                 token = token->next;
 406                 if (token_type(token) != TOKEN_NUMBER)
 407                         return;
 408                 arg = atoi(token->number);
 409                 add_function_hook(func, &match_copy_to_user, INT_PTR(arg));
 410                 token = token->next;
 411         }
 412         clear_token_alloc();
 413 }
 414
 415 void check_rosenberg(int id)
 416 {
 417         if (option_project != PROJ_KERNEL)
 418                 return;
 419         my_whole_id = id;
 420
 421         add_function_hook("memset", &match_clear, INT_PTR(0));
 422         add_function_hook("memcpy", &match_clear, INT_PTR(0));
 423         add_function_hook("memzero", &match_clear, INT_PTR(0));
 424         add_function_hook("__memset", &match_clear, INT_PTR(0));
 425         add_function_hook("__memcpy", &match_clear, INT_PTR(0));
 426         add_function_hook("__memzero", &match_clear, INT_PTR(0));
 427         add_function_hook("__builtin_memset", &match_clear, INT_PTR(0));
 428         add_function_hook("__builtin_memcpy", &match_clear, INT_PTR(0));
 429
 430         register_clears_argument();
 431         select_return_states_hook(BUF_CLEARED, &db_param_cleared);
 432
 433         register_copy_funcs_from_file();
 434 }
 435
 436 void check_rosenberg2(int id)
 437 {
 438         if (option_project != PROJ_KERNEL)
 439                 return;
 440
 441         my_member_id = id;
 442         set_dynamic_states(my_member_id);
 443         add_extra_mod_hook(&extra_mod_hook);
 444 }
 445
 446 void check_rosenberg3(int id)
 447 {
 448         if (option_project != PROJ_KERNEL)
 449                 return;
 450
 451         skb_put_id = id;
 452         set_dynamic_states(skb_put_id);
 453         add_function_assign_hook("skb_put", &match_skb_put, NULL);
 454         add_hook(&match_return_skb_put, RETURN_HOOK);
 455 }
 456