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                         scoped_state(name, my_id, sym);
 160                 } else {
 161                         assign_parent(sym);
 162                 }
 163         }
 164 }
 165
 166 static int is_parent(struct expression *expr)
 167 {
 168         if (expr->type == EXPR_DEREF)
 169                 return 0;
 170         return 1;
 171 }
 172
 173 static void match_assign(struct expression *expr)
 174 {
 175         struct expression *left, *right;
 176         char *left_name = NULL;
 177         char *right_name = NULL;
 178         struct symbol *left_sym, *right_sym;
 179         struct smatch_state *state;
 180
 181         left = strip_expr(expr->left);
 182         left_name = get_variable_from_expr_complex(left, &left_sym);
 183
 184         right = strip_expr(expr->right);
 185         if (left_name && left_sym && is_allocation(right) &&
 186             !(left_sym->ctype.modifiers &
 187               (MOD_NONLOCAL | MOD_STATIC | MOD_ADDRESSABLE)) &&
 188             !parent_is_assigned(left_sym)) {
 189                 set_state(left_name, my_id, left_sym, &malloced);
 190                 goto exit;
 191         }
 192
 193         right_name = get_variable_from_expr_complex(right, &right_sym);
 194
 195         if (right_name && (state = get_state(right_name, my_id, right_sym))) {
 196                 if (state == &isfree)
 197                         smatch_msg("error: assigning freed pointer");
 198                 set_state(right_name, my_id, right_sym, &assigned);
 199         }
 200
 201         if (is_freed(left_name, left_sym)) {
 202                 set_state(left_name, my_id, left_sym, &unfree);
 203         }
 204         if (left_name && is_parent(left))
 205                 assign_parent(left_sym);
 206         if (right_name && is_parent(right))
 207                 assign_parent(right_sym);
 208 exit:
 209         free_string(left_name);
 210         free_string(right_name);
 211 }
 212
 213 static int is_null(const char *name, struct symbol *sym)
 214 {
 215         struct smatch_state *state;
 216
 217         state = get_state(name, my_id, sym);
 218         if (state && !strcmp(state->name, "isnull"))
 219                 return 1;
 220         return 0;
 221 }
 222
 223 static void match_free_func(const char *fn, struct expression *expr, void *data)
 224 {
 225         struct expression *ptr_expr;
 226         char *ptr_name;
 227         struct symbol *ptr_sym;
 228         int arg_num = PTR_INT(data);
 229
 230         ptr_expr = get_argument_from_call_expr(expr->args, arg_num);
 231         ptr_name = get_variable_from_expr_complex(ptr_expr, &ptr_sym);
 232         if (is_freed(ptr_name, ptr_sym) && !is_null(ptr_name, ptr_sym)) {
 233                 smatch_msg("error: double free of %s", ptr_name);
 234         }
 235         set_state(ptr_name, my_id, ptr_sym, &isfree);
 236         free_string(ptr_name);
 237 }
 238
 239 static int possibly_allocated(struct state_list *slist)
 240 {
 241         struct sm_state *tmp;
 242
 243         FOR_EACH_PTR(slist, tmp) {
 244                 if (tmp->state == &allocated)
 245                         return 1;
 246                 if (tmp->state == &malloced)
 247                         return 1;
 248         } END_FOR_EACH_PTR(tmp);
 249         return 0;
 250 }
 251
 252 static void check_for_allocated(void)
 253 {
 254         struct state_list *slist;
 255         struct sm_state *tmp;
 256
 257         slist = get_all_states(my_id);
 258         FOR_EACH_PTR(slist, tmp) {
 259                 if (possibly_allocated(tmp->possible) &&
 260                     !is_null(tmp->name, tmp->sym) &&
 261                     !is_argument(tmp->sym) &&
 262                     !parent_is_assigned(tmp->sym))
 263                         smatch_msg("error: memery leak of %s", tmp->name);
 264         } END_FOR_EACH_PTR(tmp);
 265         free_slist(&slist);
 266 }
 267
 268 static void match_return(struct statement *stmt)
 269 {
 270         char *name;
 271         struct symbol *sym;
 272
 273         name = get_variable_from_expr_complex(stmt->ret_value, &sym);
 274         if (sym)
 275                 assign_parent(sym);
 276         free_string(name);
 277         check_for_allocated();
 278 }
 279
 280 static void set_new_true_false_paths(const char *name, struct symbol *sym)
 281 {
 282         struct smatch_state *tmp;
 283
 284         tmp = get_state(name, my_id, sym);
 285
 286         if (!tmp) {
 287                 return;
 288         }
 289
 290         if (tmp == &isfree) {
 291                 smatch_msg("warn: why do you care about freed memory?");
 292         }
 293
 294         if (tmp == &assigned) {
 295                 /* we don't care about assigned pointers any more */
 296                 return;
 297         }
 298         set_true_false_states(name, my_id, sym, &allocated, &isnull);
 299 }
 300
 301 static void match_condition(struct expression *expr)
 302 {
 303         struct symbol *sym;
 304         char *name;
 305
 306         expr = strip_expr(expr);
 307         switch(expr->type) {
 308         case EXPR_PREOP:
 309         case EXPR_SYMBOL:
 310         case EXPR_DEREF:
 311                 name = get_variable_from_expr_complex(expr, &sym);
 312                 if (!name)
 313                         return;
 314                 set_new_true_false_paths(name, sym);
 315                 free_string(name);
 316                 return;
 317         case EXPR_ASSIGNMENT:
 318                  /* You have to deal with stuff like if (a = b = c) */
 319                 match_condition(expr->right);
 320                 match_condition(expr->left);
 321                 return;
 322         default:
 323                 return;
 324         }
 325 }
 326
 327 static void match_function_call(struct expression *expr)
 328 {
 329         struct expression *tmp;
 330         struct symbol *sym;
 331         char *name;
 332         struct sm_state *state;
 333
 334         FOR_EACH_PTR(expr->args, tmp) {
 335                 tmp = strip_expr(tmp);
 336                 name = get_variable_from_expr_complex(tmp, &sym);
 337                 if (!name)
 338                         continue;
 339                 if ((state = get_sm_state(name, my_id, sym))) {
 340                         if (possibly_allocated(state->possible)) {
 341                                 set_state(name, my_id, sym, &assigned);
 342                         }
 343                 }
 344                 assign_parent(sym);
 345                 free_string(name);
 346         } END_FOR_EACH_PTR(tmp);
 347 }
 348
 349 static void match_dereferences(struct expression *expr)
 350 {
 351         char *deref = NULL;
 352         struct symbol *sym = NULL;
 353
 354         deref = get_variable_from_expr(expr->deref->unop, &sym);
 355         if (!deref)
 356                 return;
 357         if (is_freed(deref, sym)) {
 358                 smatch_msg("error: dereferencing freed memory '%s'", deref);
 359                 set_state(deref, my_id, sym, &unfree);
 360         }
 361         free_string(deref);
 362 }
 363
 364 static void match_end_func(struct symbol *sym)
 365 {
 366         check_for_allocated();
 367         free_trackers_and_list(&arguments);
 368 }
 369
 370 static void register_funcs_from_file(void)
 371 {
 372         struct token *token;
 373         const char *func;
 374         int arg;
 375
 376         token = get_tokens_file("kernel.frees_argument");
 377         if (!token)
 378                 return;
 379         if (token_type(token) != TOKEN_STREAMBEGIN)
 380                 return;
 381         token = token->next;
 382         while (token_type(token) != TOKEN_STREAMEND) {
 383                 if (token_type(token) != TOKEN_IDENT)
 384                         return;
 385                 func = show_ident(token->ident);
 386                 token = token->next;
 387                 if (token_type(token) != TOKEN_NUMBER)
 388                         return;
 389                 arg = atoi(token->number);
 390                 add_function_hook(func, &match_free_func, INT_PTR(arg));
 391                 token = token->next;
 392         }
 393         clear_token_alloc();
 394 }
 395
 396 void check_memory(int id)
 397 {
 398         my_id = id;
 399         add_unmatched_state_hook(my_id, &unmatched_state);
 400         add_hook(&match_function_def, FUNC_DEF_HOOK);
 401         add_hook(&match_declarations, DECLARATION_HOOK);
 402         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 403         add_hook(&match_condition, CONDITION_HOOK);
 404         add_hook(&match_dereferences, DEREF_HOOK);
 405         add_hook(&match_assign, ASSIGNMENT_HOOK);
 406         add_hook(&match_return, RETURN_HOOK);
 407         add_hook(&match_end_func, END_FUNC_HOOK);
 408         add_function_hook("kfree", &match_free_func, (void *)0);
 409         register_funcs_from_file();
 410 }