check_kernel.c

   1 /*
   2  * Copyright (C) 2010 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  * This is kernel specific stuff for smatch_extra.
  20  */
  21
  22 #include "scope.h"
  23 #include "smatch.h"
  24 #include "smatch_extra.h"
  25
  26 static sval_t err_ptr_min = {
  27         .type = &ptr_ctype,
  28         .value = -4095,
  29 };
  30 static sval_t err_ptr_max = {
  31         .type = &ptr_ctype,
  32         .value = -1,
  33 };
  34 static sval_t null_ptr = {
  35         .type = &ptr_ctype,
  36         .value = 0,
  37 };
  38
  39 static int implied_err_cast_return(struct expression *call, void *unused, struct range_list **rl)
  40 {
  41         struct expression *arg;
  42
  43         arg = get_argument_from_call_expr(call->args, 0);
  44         if (!get_implied_rl(arg, rl)) {
  45                 *rl = alloc_rl(err_ptr_min, err_ptr_max);
  46                 *rl = cast_rl(get_type(arg), *rl);
  47         }
  48         return 1;
  49 }
  50
  51 static void hack_ERR_PTR(struct symbol *sym)
  52 {
  53         struct symbol *arg;
  54         struct smatch_state *estate;
  55         struct range_list *after;
  56         sval_t low_error = {
  57                 .type = &long_ctype,
  58                 .value = -4095,
  59         };
  60         sval_t minus_one = {
  61                 .type = &long_ctype,
  62                 .value = -1,
  63         };
  64         sval_t zero = {
  65                 .type = &long_ctype,
  66                 .value = 0,
  67         };
  68
  69         if (!sym || !sym->ident)
  70                 return;
  71         if (strcmp(sym->ident->name, "ERR_PTR") != 0)
  72                 return;
  73
  74         arg = first_ptr_list((struct ptr_list *)sym->ctype.base_type->arguments);
  75         if (!arg || !arg->ident)
  76                 return;
  77
  78         estate = get_state(SMATCH_EXTRA, arg->ident->name, arg);
  79         if (!estate) {
  80                 after = alloc_rl(low_error, minus_one);
  81         } else {
  82                 after = rl_intersection(estate_rl(estate), alloc_rl(low_error, zero));
  83                 if (rl_equiv(estate_rl(estate), after))
  84                         return;
  85         }
  86         set_state(SMATCH_EXTRA, arg->ident->name, arg, alloc_estate_rl(after));
  87 }
  88
  89 static void match_param_valid_ptr(const char *fn, struct expression *call_expr,
  90                         struct expression *assign_expr, void *_param)
  91 {
  92         int param = PTR_INT(_param);
  93         struct expression *arg;
  94         struct smatch_state *pre_state;
  95         struct smatch_state *end_state;
  96         struct range_list *rl;
  97
  98         arg = get_argument_from_call_expr(call_expr->args, param);
  99         pre_state = get_state_expr(SMATCH_EXTRA, arg);
 100         if (estate_rl(pre_state)) {
 101                 rl = estate_rl(pre_state);
 102                 rl = remove_range(rl, null_ptr, null_ptr);
 103                 rl = remove_range(rl, err_ptr_min, err_ptr_max);
 104         } else {
 105                 rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 106         }
 107         end_state = alloc_estate_rl(rl);
 108         set_extra_expr_nomod(arg, end_state);
 109 }
 110
 111 static void match_param_err_or_null(const char *fn, struct expression *call_expr,
 112                         struct expression *assign_expr, void *_param)
 113 {
 114         int param = PTR_INT(_param);
 115         struct expression *arg;
 116         struct range_list *rl;
 117         struct smatch_state *pre_state;
 118         struct smatch_state *end_state;
 119
 120         arg = get_argument_from_call_expr(call_expr->args, param);
 121         pre_state = get_state_expr(SMATCH_EXTRA, arg);
 122         call_results_to_rl(call_expr, &ptr_ctype, "0,(-4095)-(-1)", &rl);
 123         rl = rl_intersection(estate_rl(pre_state), rl);
 124         rl = cast_rl(get_type(arg), rl);
 125         end_state = alloc_estate_rl(rl);
 126         set_extra_expr_nomod(arg, end_state);
 127 }
 128
 129 static void match_not_err(const char *fn, struct expression *call_expr,
 130                         struct expression *assign_expr, void *unused)
 131 {
 132         struct expression *arg;
 133         struct smatch_state *pre_state;
 134         struct range_list *rl;
 135
 136         arg = get_argument_from_call_expr(call_expr->args, 0);
 137         pre_state = get_state_expr(SMATCH_EXTRA, arg);
 138         if (estate_rl(pre_state))
 139                 rl = rl_intersection(estate_rl(pre_state), valid_ptr_rl);
 140         else
 141                 rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 142         rl = cast_rl(get_type(arg), rl);
 143         set_extra_expr_nomod(arg, alloc_estate_rl(rl));
 144 }
 145
 146 static void match_err(const char *fn, struct expression *call_expr,
 147                         struct expression *assign_expr, void *unused)
 148 {
 149         struct expression *arg;
 150         struct smatch_state *pre_state;
 151         struct range_list *rl;
 152
 153         arg = get_argument_from_call_expr(call_expr->args, 0);
 154         pre_state = get_state_expr(SMATCH_EXTRA, arg);
 155         rl = estate_rl(pre_state);
 156         if (!rl)
 157                 rl = alloc_rl(err_ptr_min, err_ptr_max);
 158         rl = rl_intersection(rl, alloc_rl(err_ptr_min, err_ptr_max));
 159         rl = cast_rl(get_type(arg), rl);
 160         set_extra_expr_nomod(arg, alloc_estate_rl(rl));
 161 }
 162
 163 static void match_container_of_macro(const char *fn, struct expression *expr, void *unused)
 164 {
 165         set_extra_expr_mod(expr->left, alloc_estate_range(valid_ptr_min_sval, valid_ptr_max_sval));
 166 }
 167
 168 static void match_container_of(struct expression *expr)
 169 {
 170         struct expression *right = expr->right;
 171         char *macro;
 172
 173         /*
 174          * The problem here is that sometimes the container_of() macro is itself
 175          * inside a macro and get_macro() only returns the name of the outside
 176          * macro.
 177          */
 178
 179         /*
 180          * This actually an expression statement assignment but smatch_flow
 181          * pre-mangles it for us so we only get the last chunk:
 182          * sk = (typeof(sk))((char *)__mptr - offsetof(...))
 183          */
 184
 185         macro = get_macro_name(right->pos);
 186         if (!macro)
 187                 return;
 188         if (right->type != EXPR_CAST)
 189                 return;
 190         right = strip_expr(right);
 191         if (right->type != EXPR_BINOP || right->op != '-' ||
 192             right->left->type != EXPR_CAST)
 193                 return;
 194         right = strip_expr(right->left);
 195         if (right->type != EXPR_SYMBOL)
 196                 return;
 197         if (!right->symbol->ident ||
 198             strcmp(right->symbol->ident->name, "__mptr") != 0)
 199                 return;
 200         set_extra_expr_mod(expr->left, alloc_estate_range(valid_ptr_min_sval, valid_ptr_max_sval));
 201 }
 202
 203 static int match_next_bit(struct expression *call, void *unused, struct range_list **rl)
 204 {
 205         struct expression *start_arg;
 206         struct expression *size_arg;
 207         struct symbol *type;
 208         sval_t min, max, tmp;
 209
 210         size_arg = get_argument_from_call_expr(call->args, 1);
 211         /* btw. there isn't a start_arg for find_first_bit() */
 212         start_arg = get_argument_from_call_expr(call->args, 2);
 213
 214         type = get_type(call);
 215         min = sval_type_val(type, 0);
 216         max = sval_type_val(type, sizeof(long long) * 8);
 217
 218         if (get_implied_max(size_arg, &tmp) && tmp.uvalue < max.value)
 219                 max = tmp;
 220         if (start_arg && get_implied_min(start_arg, &tmp) && !sval_is_negative(tmp))
 221                 min = tmp;
 222         if (sval_cmp(min, max) > 0)
 223                 max = min;
 224         min = sval_cast(type, min);
 225         max = sval_cast(type, max);
 226         *rl = alloc_rl(min, max);
 227         return 1;
 228 }
 229
 230 static int match_fls(struct expression *call, void *unused, struct range_list **rl)
 231 {
 232         struct expression *arg;
 233         struct range_list *arg_rl;
 234         sval_t zero = {};
 235         sval_t start = {
 236                 .type = &int_ctype,
 237                 .value = 0,
 238         };
 239         sval_t end = {
 240                 .type = &int_ctype,
 241                 .value = 32,
 242         };
 243         sval_t sval;
 244
 245         arg = get_argument_from_call_expr(call->args, 0);
 246         if (!get_implied_rl(arg, &arg_rl))
 247                 return 0;
 248         if (rl_to_sval(arg_rl, &sval)) {
 249                 int i;
 250
 251                 for (i = 63; i >= 0; i--) {
 252                         if (sval.uvalue & 1ULL << i)
 253                                 break;
 254                 }
 255                 sval.value = i + 1;
 256                 *rl = alloc_rl(sval, sval);
 257                 return 1;
 258         }
 259         zero.type = rl_type(arg_rl);
 260         if (!rl_has_sval(arg_rl, zero))
 261                 start.value = 1;
 262         *rl = alloc_rl(start, end);
 263         return 1;
 264 }
 265
 266
 267
 268 static void find_module_init_exit(struct symbol_list *sym_list)
 269 {
 270         struct symbol *sym;
 271         struct symbol *fn;
 272         struct statement *stmt;
 273         char *name;
 274         int init;
 275         int count;
 276
 277         /*
 278          * This is more complicated because Sparse ignores the "alias"
 279          * attribute.  I search backwards because module_init() is normally at
 280          * the end of the file.
 281          */
 282         count = 0;
 283         FOR_EACH_PTR_REVERSE(sym_list, sym) {
 284                 if (sym->type != SYM_NODE)
 285                         continue;
 286                 if (!(sym->ctype.modifiers & MOD_STATIC))
 287                         continue;
 288                 fn = get_base_type(sym);
 289                 if (!fn)
 290                         continue;
 291                 if (fn->type != SYM_FN)
 292                         continue;
 293                 if (!sym->ident)
 294                         continue;
 295                 if (!fn->inline_stmt)
 296                         continue;
 297                 if (strcmp(sym->ident->name, "__inittest") == 0)
 298                         init = 1;
 299                 else if (strcmp(sym->ident->name, "__exittest") == 0)
 300                         init = 0;
 301                 else
 302                         continue;
 303
 304                 count++;
 305
 306                 stmt = first_ptr_list((struct ptr_list *)fn->inline_stmt->stmts);
 307                 if (!stmt || stmt->type != STMT_RETURN)
 308                         continue;
 309                 name = expr_to_var(stmt->ret_value);
 310                 if (!name)
 311                         continue;
 312                 if (init)
 313                         sql_insert_function_ptr(name, "(struct module)->init");
 314                 else
 315                         sql_insert_function_ptr(name, "(struct module)->exit");
 316                 free_string(name);
 317                 if (count >= 2)
 318                         return;
 319         } END_FOR_EACH_PTR_REVERSE(sym);
 320 }
 321
 322 static void match_end_file(struct symbol_list *sym_list)
 323 {
 324         struct symbol *sym;
 325
 326         /* find the last static symbol in the file */
 327         FOR_EACH_PTR_REVERSE(sym_list, sym) {
 328                 if (!(sym->ctype.modifiers & MOD_STATIC))
 329                         continue;
 330                 if (!sym->scope)
 331                         continue;
 332                 find_module_init_exit(sym->scope->symbols);
 333                 return;
 334         } END_FOR_EACH_PTR_REVERSE(sym);
 335 }
 336
 337 static struct expression *get_val_expr(struct expression *expr)
 338 {
 339         struct symbol *sym, *val;
 340
 341         if (expr->type != EXPR_DEREF)
 342                 return NULL;
 343         expr = expr->deref;
 344         if (expr->type != EXPR_SYMBOL)
 345                 return NULL;
 346         if (strcmp(expr->symbol_name->name, "__u") != 0)
 347                 return NULL;
 348         sym = get_base_type(expr->symbol);
 349         val = first_ptr_list((struct ptr_list *)sym->symbol_list);
 350         if (!val || strcmp(val->ident->name, "__val") != 0)
 351                 return NULL;
 352         return member_expression(expr, '.', val->ident);
 353 }
 354
 355 static void match__write_once_size(const char *fn, struct expression *call,
 356                                void *unused)
 357 {
 358         struct expression *dest, *data, *assign;
 359         struct range_list *rl;
 360
 361         dest = get_argument_from_call_expr(call->args, 0);
 362         if (dest->type != EXPR_PREOP || dest->op != '&')
 363                 return;
 364         dest = strip_expr(dest->unop);
 365
 366         data = get_argument_from_call_expr(call->args, 1);
 367         data = get_val_expr(data);
 368         if (!data)
 369                 return;
 370         get_absolute_rl(data, &rl);
 371         assign = assign_expression(dest, '=', data);
 372
 373         __in_fake_assign++;
 374         __split_expr(assign);
 375         __in_fake_assign--;
 376 }
 377
 378 static void match__read_once_size(const char *fn, struct expression *call,
 379                                void *unused)
 380 {
 381         struct expression *dest, *data, *assign;
 382         struct symbol *type, *val_sym;
 383
 384         /*
 385          * We want to change:
 386          *      __read_once_size_nocheck(&(x), __u.__c, sizeof(x));
 387          * into a fake assignment:
 388          *      __u.val = x;
 389          *
 390          */
 391
 392         data = get_argument_from_call_expr(call->args, 0);
 393         if (data->type != EXPR_PREOP || data->op != '&')
 394                 return;
 395         data = strip_parens(data->unop);
 396
 397         dest = get_argument_from_call_expr(call->args, 1);
 398         if (dest->type != EXPR_DEREF || dest->op != '.')
 399                 return;
 400         if (!dest->member || strcmp(dest->member->name, "__c") != 0)
 401                 return;
 402         dest = dest->deref;
 403         type = get_type(dest);
 404         if (!type)
 405                 return;
 406         val_sym = first_ptr_list((struct ptr_list *)type->symbol_list);
 407         dest = member_expression(dest, '.', val_sym->ident);
 408
 409         assign = assign_expression(dest, '=', data);
 410         __in_fake_assign++;
 411         __split_expr(assign);
 412         __in_fake_assign--;
 413 }
 414
 415 void check_kernel(int id)
 416 {
 417         if (option_project != PROJ_KERNEL)
 418                 return;
 419
 420         add_implied_return_hook("ERR_PTR", &implied_err_cast_return, NULL);
 421         add_implied_return_hook("ERR_CAST", &implied_err_cast_return, NULL);
 422         add_implied_return_hook("PTR_ERR", &implied_err_cast_return, NULL);
 423         add_hook(hack_ERR_PTR, AFTER_DEF_HOOK);
 424         return_implies_state("IS_ERR_OR_NULL", 0, 0, &match_param_valid_ptr, (void *)0);
 425         return_implies_state("IS_ERR_OR_NULL", 1, 1, &match_param_err_or_null, (void *)0);
 426         return_implies_state("IS_ERR", 0, 0, &match_not_err, NULL);
 427         return_implies_state("IS_ERR", 1, 1, &match_err, NULL);
 428         return_implies_state("tomoyo_memory_ok", 1, 1, &match_param_valid_ptr, (void *)0);
 429
 430         add_macro_assign_hook_extra("container_of", &match_container_of_macro, NULL);
 431         add_hook(match_container_of, ASSIGNMENT_HOOK);
 432
 433         add_implied_return_hook("find_next_bit", &match_next_bit, NULL);
 434         add_implied_return_hook("find_next_zero_bit", &match_next_bit, NULL);
 435         add_implied_return_hook("find_first_bit", &match_next_bit, NULL);
 436         add_implied_return_hook("find_first_zero_bit", &match_next_bit, NULL);
 437
 438         add_implied_return_hook("fls", &match_fls, NULL);
 439         add_implied_return_hook("fls64", &match_fls, NULL);
 440
 441         add_function_hook("__ftrace_bad_type", &__match_nullify_path_hook, NULL);
 442         add_function_hook("__write_once_size", &match__write_once_size, NULL);
 443
 444         add_function_hook("__read_once_size", &match__read_once_size, NULL);
 445         add_function_hook("__read_once_size_nocheck", &match__read_once_size, NULL);
 446
 447         if (option_info)
 448                 add_hook(match_end_file, END_FILE_HOOK);
 449 }