check_memory.c

   1 /*
   2  * sparse/check_memory.c
   3  *
   4  * Copyright (C) 2008 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include <fcntl.h>
  11 #include <unistd.h>
  12 #include "parse.h"
  13 #include "smatch.h"
  14 #include "smatch_slist.h"
  15
  16 static int my_id;
  17
  18 STATE(allocated);
  19 STATE(assigned);
  20 STATE(isfree);
  21 STATE(malloced);
  22 STATE(isnull);
  23 STATE(unfree);
  24
  25 /*
  26   malloced --> allocated --> assigned --> isfree +
  27             \-> isnull.    \-> isfree +
  28
  29   isfree --> unfree.
  30           \-> isnull.
  31 */
  32
  33 static struct tracker_list *arguments;
  34
  35 static const char *allocation_funcs[] = {
  36         "malloc",
  37         "kmalloc",
  38         "kzalloc",
  39         NULL,
  40 };
  41
  42 static char *get_parent_name(struct symbol *sym)
  43 {
  44         static char buf[256];
  45
  46         if (!sym || !sym->ident)
  47                 return NULL;
  48
  49         snprintf(buf, 255, "-%s", sym->ident->name);
  50         buf[255] = '\0';
  51         return alloc_string(buf);
  52 }
  53
  54 static int is_parent_sym(const char *name)
  55 {
  56         if (!strncmp(name, "-", 1))
  57                 return 1;
  58         return 0;
  59 }
  60
  61 static struct smatch_state *unmatched_state(struct sm_state *sm)
  62 {
  63         if (is_parent_sym(sm->name))
  64                 return &assigned;
  65         return &undefined;
  66 }
  67
  68 static void assign_parent(struct symbol *sym)
  69 {
  70         char *name;
  71
  72         name = get_parent_name(sym);
  73         if (!name)
  74                 return;
  75         set_state(name, my_id, sym, &assigned);
  76         free_string(name);
  77 }
  78
  79 static int parent_is_assigned(struct symbol *sym)
  80 {
  81         struct smatch_state *state;
  82         char *name;
  83
  84         name = get_parent_name(sym);
  85         if (!name)
  86                 return 0;
  87         state = get_state(name, my_id, sym);
  88         free_string(name);
  89         if (state == &assigned)
  90                 return 1;
  91         return 0;
  92 }
  93
  94 static int is_allocation(struct expression *expr)
  95 {
  96         char *fn_name;
  97         int i;
  98
  99         if (expr->type != EXPR_CALL)
 100                 return 0;
 101
 102         if (!(fn_name = get_variable_from_expr(expr->fn, NULL)))
 103                 return 0;
 104
 105         for (i = 0; allocation_funcs[i]; i++) {
 106                 if (!strcmp(fn_name, allocation_funcs[i])) {
 107                         free_string(fn_name);
 108                         return 1;
 109                 }
 110         }
 111         free_string(fn_name);
 112         return 0;
 113 }
 114
 115 static int is_freed(const char *name, struct symbol *sym)
 116 {
 117         struct state_list *slist;
 118
 119         slist = get_possible_states(name, my_id, sym);
 120         if (slist_has_state(slist, &isfree)) {
 121                 return 1;
 122         }
 123         return 0;
 124 }
 125
 126 static int is_argument(struct symbol *sym)
 127 {
 128         struct tracker *arg;
 129
 130         FOR_EACH_PTR(arguments, arg) {
 131                 if (arg->sym == sym)
 132                         return 1;
 133         } END_FOR_EACH_PTR(arg);
 134         return 0;
 135 }
 136
 137 static void match_function_def(struct symbol *sym)
 138 {
 139         struct symbol *arg;
 140
 141         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 142                 add_tracker(&arguments, (arg->ident?arg->ident->name:"NULL"), my_id, arg);
 143         } END_FOR_EACH_PTR(arg);
 144 }
 145
 146 static void match_declarations(struct symbol *sym)
 147 {
 148         const char *name;
 149
 150         if ((get_base_type(sym))->type == SYM_ARRAY) {
 151                 return;
 152         }
 153
 154         name = sym->ident->name;
 155
 156         if (sym->initializer) {
 157                 if (is_allocation(sym->initializer)) {
 158                         set_state(name, my_id, sym, &malloced);
 159                 } else {
 160                         assign_parent(sym);
 161                 }
 162         }
 163 }
 164
 165 static int is_parent(struct expression *expr)
 166 {
 167         if (expr->type == EXPR_DEREF)
 168                 return 0;
 169         return 1;
 170 }
 171
 172 static void match_assign(struct expression *expr)
 173 {
 174         struct expression *left, *right;
 175         char *left_name = NULL;
 176         char *right_name = NULL;
 177         struct symbol *left_sym, *right_sym;
 178         struct smatch_state *state;
 179
 180         left = strip_expr(expr->left);
 181         left_name = get_variable_from_expr_complex(left, &left_sym);
 182
 183         right = strip_expr(expr->right);
 184         if (left_name && left_sym && is_allocation(right) &&
 185             !(left_sym->ctype.modifiers &
 186               (MOD_NONLOCAL | MOD_STATIC | MOD_ADDRESSABLE)) &&
 187             !parent_is_assigned(left_sym)) {
 188                 set_state(left_name, my_id, left_sym, &malloced);
 189                 goto exit;
 190         }
 191
 192         right_name = get_variable_from_expr_complex(right, &right_sym);
 193
 194         if (right_name && (state = get_state(right_name, my_id, right_sym))) {
 195                 if (state == &isfree)
 196                         smatch_msg("error: assigning freed pointer");
 197                 set_state(right_name, my_id, right_sym, &assigned);
 198         }
 199
 200         if (is_freed(left_name, left_sym)) {
 201                 set_state(left_name, my_id, left_sym, &unfree);
 202         }
 203         if (left_name && is_parent(left))
 204                 assign_parent(left_sym);
 205         if (right_name && is_parent(right))
 206                 assign_parent(right_sym);
 207 exit:
 208         free_string(left_name);
 209         free_string(right_name);
 210 }
 211
 212 static int is_null(const char *name, struct symbol *sym)
 213 {
 214         struct smatch_state *state;
 215
 216         state = get_state(name, my_id, sym);
 217         if (state && !strcmp(state->name, "isnull"))
 218                 return 1;
 219         return 0;
 220 }
 221
 222 static void match_free_func(const char *fn, struct expression *expr, void *data)
 223 {
 224         struct expression *ptr_expr;
 225         char *ptr_name;
 226         struct symbol *ptr_sym;
 227         int arg_num = PTR_INT(data);
 228
 229         ptr_expr = get_argument_from_call_expr(expr->args, arg_num);
 230         ptr_name = get_variable_from_expr_complex(ptr_expr, &ptr_sym);
 231         if (is_freed(ptr_name, ptr_sym) && !is_null(ptr_name, ptr_sym)) {
 232                 smatch_msg("error: double free of %s", ptr_name);
 233         }
 234         set_state(ptr_name, my_id, ptr_sym, &isfree);
 235         free_string(ptr_name);
 236 }
 237
 238 static int possibly_allocated(struct state_list *slist)
 239 {
 240         struct sm_state *tmp;
 241
 242         FOR_EACH_PTR(slist, tmp) {
 243                 if (tmp->state == &allocated)
 244                         return 1;
 245                 if (tmp->state == &malloced)
 246                         return 1;
 247         } END_FOR_EACH_PTR(tmp);
 248         return 0;
 249 }
 250
 251 static void check_for_allocated(void)
 252 {
 253         struct state_list *slist;
 254         struct sm_state *tmp;
 255
 256         slist = get_all_states(my_id);
 257         FOR_EACH_PTR(slist, tmp) {
 258                 if (possibly_allocated(tmp->possible) &&
 259                     !is_null(tmp->name, tmp->sym) &&
 260                     !is_argument(tmp->sym) &&
 261                     !parent_is_assigned(tmp->sym))
 262                         smatch_msg("error: memery leak of %s", tmp->name);
 263         } END_FOR_EACH_PTR(tmp);
 264         free_slist(&slist);
 265 }
 266
 267 static void match_return(struct statement *stmt)
 268 {
 269         char *name;
 270         struct symbol *sym;
 271
 272         name = get_variable_from_expr_complex(stmt->ret_value, &sym);
 273         if (sym)
 274                 assign_parent(sym);
 275         free_string(name);
 276         check_for_allocated();
 277 }
 278
 279 static void set_new_true_false_paths(const char *name, struct symbol *sym)
 280 {
 281         struct smatch_state *tmp;
 282
 283         tmp = get_state(name, my_id, sym);
 284
 285         if (!tmp) {
 286                 return;
 287         }
 288
 289         if (tmp == &isfree) {
 290                 smatch_msg("warn: why do you care about freed memory?");
 291         }
 292
 293         if (tmp == &assigned) {
 294                 /* we don't care about assigned pointers any more */
 295                 return;
 296         }
 297         set_true_false_states(name, my_id, sym, &allocated, &isnull);
 298 }
 299
 300 static void match_condition(struct expression *expr)
 301 {
 302         struct symbol *sym;
 303         char *name;
 304
 305         expr = strip_expr(expr);
 306         switch(expr->type) {
 307         case EXPR_PREOP:
 308         case EXPR_SYMBOL:
 309         case EXPR_DEREF:
 310                 name = get_variable_from_expr_complex(expr, &sym);
 311                 if (!name)
 312                         return;
 313                 set_new_true_false_paths(name, sym);
 314                 free_string(name);
 315                 return;
 316         case EXPR_ASSIGNMENT:
 317                  /* You have to deal with stuff like if (a = b = c) */
 318                 match_condition(expr->right);
 319                 match_condition(expr->left);
 320                 return;
 321         default:
 322                 return;
 323         }
 324 }
 325
 326 static void match_function_call(struct expression *expr)
 327 {
 328         struct expression *tmp;
 329         struct symbol *sym;
 330         char *name;
 331         struct sm_state *state;
 332
 333         FOR_EACH_PTR(expr->args, tmp) {
 334                 tmp = strip_expr(tmp);
 335                 name = get_variable_from_expr_complex(tmp, &sym);
 336                 if (!name)
 337                         continue;
 338                 if ((state = get_sm_state(name, my_id, sym))) {
 339                         if (possibly_allocated(state->possible)) {
 340                                 set_state(name, my_id, sym, &assigned);
 341                         }
 342                 }
 343                 assign_parent(sym);
 344                 free_string(name);
 345         } END_FOR_EACH_PTR(tmp);
 346 }
 347
 348 static void match_dereferences(struct expression *expr)
 349 {
 350         char *deref = NULL;
 351         struct symbol *sym = NULL;
 352
 353         deref = get_variable_from_expr(expr->deref->unop, &sym);
 354         if (!deref)
 355                 return;
 356         if (is_freed(deref, sym)) {
 357                 smatch_msg("error: dereferencing freed memory '%s'", deref);
 358                 set_state(deref, my_id, sym, &unfree);
 359         }
 360         free_string(deref);
 361 }
 362
 363 static void match_end_func(struct symbol *sym)
 364 {
 365         check_for_allocated();
 366         free_trackers_and_list(&arguments);
 367 }
 368
 369 static void register_funcs_from_file(void)
 370 {
 371         struct token *token;
 372         const char *func;
 373         int arg;
 374
 375         token = get_tokens_file("kernel.frees_argument");
 376         if (!token)
 377                 return;
 378         if (token_type(token) != TOKEN_STREAMBEGIN)
 379                 return;
 380         token = token->next;
 381         while (token_type(token) != TOKEN_STREAMEND) {
 382                 if (token_type(token) != TOKEN_IDENT)
 383                         return;
 384                 func = show_ident(token->ident);
 385                 token = token->next;
 386                 if (token_type(token) != TOKEN_NUMBER)
 387                         return;
 388                 arg = atoi(token->number);
 389                 add_function_hook(func, &match_free_func, INT_PTR(arg));
 390                 token = token->next;
 391         }
 392         clear_token_alloc();
 393 }
 394
 395 void check_memory(int id)
 396 {
 397         my_id = id;
 398         add_unmatched_state_hook(my_id, &unmatched_state);
 399         add_hook(&match_function_def, FUNC_DEF_HOOK);
 400         add_hook(&match_declarations, DECLARATION_HOOK);
 401         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 402         add_hook(&match_condition, CONDITION_HOOK);
 403         add_hook(&match_dereferences, DEREF_HOOK);
 404         add_hook(&match_assign, ASSIGNMENT_HOOK);
 405         add_hook(&match_return, RETURN_HOOK);
 406         add_hook(&match_end_func, END_FUNC_HOOK);
 407         add_function_hook("kfree", &match_free_func, (void *)0);
 408         register_funcs_from_file();
 409 }