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 "parse.h"
  11 #include "smatch.h"
  12 #include "smatch_slist.h"
  13
  14 static int my_id;
  15
  16 STATE(allocated);
  17 STATE(assigned);
  18 STATE(isfree);
  19 STATE(malloced);
  20 STATE(isnull);
  21 STATE(unfree);
  22
  23 /*
  24   malloced --> allocated --> assigned --> isfree +
  25             \-> isnull.    \-> isfree +
  26
  27   isfree --> unfree.
  28           \-> isnull.
  29 */
  30
  31 struct tracker_list *arguments;
  32
  33 static const char *allocation_funcs[] = {
  34         "malloc",
  35         "kmalloc",
  36         NULL,
  37 };
  38
  39 static struct smatch_state *merge_func(const char *name, struct symbol *sym,
  40                                        struct smatch_state *s1,
  41                                        struct smatch_state *s2)
  42 {
  43         if (!strcmp(name, "-"))
  44                 return &assigned;
  45         /* this is normal merge */
  46         if (!s1 || !s2)
  47                 return &undefined;
  48         return &merged;
  49 }
  50
  51 static void assign_parent(struct symbol *sym)
  52 {
  53         set_state("-", my_id, sym, &assigned);
  54 }
  55
  56 static int parent_is_assigned(struct symbol *sym)
  57 {
  58         struct smatch_state *state;
  59
  60         state = get_state("-", my_id, sym);
  61         if (state == &assigned)
  62                 return 1;
  63         return 0;
  64 }
  65
  66 static int is_allocation(struct expression *expr)
  67 {
  68         char *fn_name;
  69         int i;
  70
  71         if (expr->type != EXPR_CALL)
  72                 return 0;
  73
  74         if (!(fn_name = get_variable_from_expr(expr->fn, NULL)))
  75                 return 0;
  76
  77         for (i = 0; allocation_funcs[i]; i++) {
  78                 if (!strcmp(fn_name, allocation_funcs[i])) {
  79                         free_string(fn_name);
  80                         return 1;
  81                 }
  82         }
  83         free_string(fn_name);
  84         return 0;
  85 }
  86
  87 static int is_freed(const char *name, struct symbol *sym)
  88 {
  89         struct state_list *slist;
  90
  91         slist = get_possible_states(name, my_id, sym);
  92         if (slist_has_state(slist, &isfree)) {
  93                 return 1;
  94         }
  95         return 0;
  96 }
  97
  98 static int is_argument(struct symbol *sym)
  99 {
 100         struct tracker *arg;
 101
 102         FOR_EACH_PTR(arguments, arg) {
 103                 if (arg->sym == sym)
 104                         return 1;
 105         } END_FOR_EACH_PTR(arg);
 106         return 0;
 107 }
 108
 109 static void match_function_def(struct symbol *sym)
 110 {
 111         struct symbol *arg;
 112
 113         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 114                 add_tracker(&arguments, (arg->ident?arg->ident->name:"NULL"), my_id, arg);
 115         } END_FOR_EACH_PTR(arg);
 116 }
 117
 118 static void match_declarations(struct symbol *sym)
 119 {
 120         const char *name;
 121
 122         if ((get_base_type(sym))->type == SYM_ARRAY) {
 123                 return;
 124         }
 125
 126         name = sym->ident->name;
 127
 128         if (sym->initializer) {
 129                 if (is_allocation(sym->initializer)) {
 130                         set_state(name, my_id, sym, &malloced);
 131                 } else {
 132                         assign_parent(sym);
 133                 }
 134         }
 135 }
 136
 137 static int is_parent(struct expression *expr)
 138 {
 139         if (expr->type == EXPR_DEREF)
 140                 return 0;
 141         return 1;
 142 }
 143
 144 static int assign_seen;
 145 static int handle_double_assign(struct expression *expr)
 146 {
 147         struct symbol *sym;
 148         char *name;
 149
 150         if (expr->right->type != EXPR_ASSIGNMENT)
 151                 return 0;
 152         assign_seen++;
 153
 154         name = get_variable_from_expr(expr->left, &sym);
 155         if (name && is_parent(expr->left))
 156                 assign_parent(sym);
 157
 158         name = get_variable_from_expr(expr->right->left, &sym);
 159         if (name && is_parent(expr->right->left))
 160                 assign_parent(sym);
 161
 162         name = get_variable_from_expr(expr->right->right, &sym);
 163         if (name && is_parent(expr->right->right))
 164                 assign_parent(sym);
 165
 166         return 1;
 167 }
 168
 169 static void match_assign(struct expression *expr)
 170 {
 171         struct expression *left, *right;
 172         char *left_name = NULL;
 173         char *right_name = NULL;
 174         struct symbol *left_sym, *right_sym;
 175         struct smatch_state *state;
 176
 177         if (assign_seen) {
 178                 assign_seen--;
 179                 return;
 180         }
 181
 182         if (handle_double_assign(expr)) {
 183                 return;
 184         }
 185
 186         left = strip_expr(expr->left);
 187         left_name = get_variable_from_expr_complex(left, &left_sym);
 188
 189         right = strip_expr(expr->right);
 190         if (left_name && left_sym && is_allocation(right) &&
 191             !(left_sym->ctype.modifiers &
 192               (MOD_NONLOCAL | MOD_STATIC | MOD_ADDRESSABLE)) &&
 193             !parent_is_assigned(left_sym)) {
 194                 set_state(left_name, my_id, left_sym, &malloced);
 195                 goto exit;
 196         }
 197
 198         right_name = get_variable_from_expr_complex(right, &right_sym);
 199
 200         if (right_name && (state = get_state(right_name, my_id, right_sym))) {
 201                 if (state == &isfree)
 202                         smatch_msg("error: assigning freed pointer");
 203                 set_state(right_name, my_id, right_sym, &assigned);
 204         }
 205
 206         if (is_freed(left_name, left_sym)) {
 207                 set_state(left_name, my_id, left_sym, &unfree);
 208         }
 209         if (left_name && is_parent(left))
 210                 assign_parent(left_sym);
 211         if (right_name && is_parent(right))
 212                 assign_parent(right_sym);
 213 exit:
 214         free_string(left_name);
 215         free_string(right_name);
 216 }
 217
 218 static int is_null(char *name, struct symbol *sym)
 219 {
 220         struct smatch_state *state;
 221
 222         /*
 223          * FIXME.  Ha ha ha... This is so wrong.
 224          * I'm pulling in data from the check_null_deref script.
 225          * I just happen to know that its ID is 3.
 226          * The correct approved way to do this is to get the data from
 227          * smatch_extra.  But right now smatch_extra doesn't track it.
 228          */
 229         state = get_state(name, my_id, sym);
 230         if (state && !strcmp(state->name, "isnull"))
 231                 return 1;
 232         return 0;
 233 }
 234
 235 static void match_kfree(struct expression *expr)
 236 {
 237         struct expression *ptr_expr;
 238         char *ptr_name;
 239         struct symbol *ptr_sym;
 240
 241         ptr_expr = get_argument_from_call_expr(expr->args, 0);
 242         ptr_name = get_variable_from_expr(ptr_expr, &ptr_sym);
 243         if (is_freed(ptr_name, ptr_sym) && !is_null(ptr_name, ptr_sym)) {
 244                 smatch_msg("error: double free of %s", ptr_name);
 245         }
 246         set_state(ptr_name, my_id, ptr_sym, &isfree);
 247         free_string(ptr_name);
 248 }
 249
 250 static int possibly_allocated(struct state_list *slist)
 251 {
 252         struct sm_state *tmp;
 253
 254         FOR_EACH_PTR(slist, tmp) {
 255                 if (tmp->state == &allocated)
 256                         return 1;
 257                 if (tmp->state == &malloced)
 258                         return 1;
 259         } END_FOR_EACH_PTR(tmp);
 260         return 0;
 261 }
 262
 263 static void check_for_allocated()
 264 {
 265         struct state_list *slist;
 266         struct sm_state *tmp;
 267
 268         slist = get_all_states(my_id);
 269         FOR_EACH_PTR(slist, tmp) {
 270                 if (possibly_allocated(tmp->possible) &&
 271                     !is_null(tmp->name, tmp->sym) &&
 272                     !is_argument(tmp->sym) &&
 273                     !parent_is_assigned(tmp->sym))
 274                         smatch_msg("error: memery leak of %s", tmp->name);
 275         } END_FOR_EACH_PTR(tmp);
 276         free_slist(&slist);
 277 }
 278
 279 static void match_return(struct statement *stmt)
 280 {
 281         char *name;
 282         struct symbol *sym;
 283
 284         name = get_variable_from_expr(stmt->ret_value, &sym);
 285         if (sym)
 286                 assign_parent(sym);
 287         free_string(name);
 288         check_for_allocated();
 289 }
 290
 291 static void set_new_true_false_paths(const char *name, struct symbol *sym)
 292 {
 293         struct smatch_state *tmp;
 294
 295         tmp = get_state(name, my_id, sym);
 296
 297         if (!tmp) {
 298                 return;
 299         }
 300
 301         if (tmp == &isfree) {
 302                 smatch_msg("warn: why do you care about freed memory?");
 303         }
 304
 305         if (tmp == &assigned) {
 306                 /* we don't care about assigned pointers any more */
 307                 return;
 308         }
 309         set_true_false_states(name, my_id, sym, &allocated, &isnull);
 310 }
 311
 312 static void match_condition(struct expression *expr)
 313 {
 314         struct symbol *sym;
 315         char *name;
 316
 317         expr = strip_expr(expr);
 318         switch(expr->type) {
 319         case EXPR_PREOP:
 320         case EXPR_SYMBOL:
 321         case EXPR_DEREF:
 322                 name = get_variable_from_expr(expr, &sym);
 323                 if (!name)
 324                         return;
 325                 set_new_true_false_paths(name, sym);
 326                 free_string(name);
 327                 return;
 328         case EXPR_ASSIGNMENT:
 329                 assign_seen++;
 330                  /* You have to deal with stuff like if (a = b = c) */
 331                 match_condition(expr->right);
 332                 match_condition(expr->left);
 333                 return;
 334         default:
 335                 return;
 336         }
 337 }
 338
 339 static void match_function_call(struct expression *expr)
 340 {
 341         struct expression *tmp;
 342         struct symbol *sym;
 343         char *name;
 344         char *fn_name;
 345         struct sm_state *state;
 346
 347         fn_name = get_variable_from_expr(expr->fn, NULL);
 348
 349         if (fn_name && !strcmp(fn_name, "kfree")) {
 350                 match_kfree(expr);
 351         }
 352
 353         FOR_EACH_PTR(expr->args, tmp) {
 354                 tmp = strip_expr(tmp);
 355                 name = get_variable_from_expr(tmp, &sym);
 356                 if (!name)
 357                         continue;
 358                 if ((state = get_sm_state(name, my_id, sym))) {
 359                         if (possibly_allocated(state->possible)) {
 360                                 set_state(name, my_id, sym, &assigned);
 361                         }
 362                 }
 363                 assign_parent(sym);
 364         } END_FOR_EACH_PTR(tmp);
 365 }
 366
 367 static void match_end_func(struct symbol *sym)
 368 {
 369         check_for_allocated();
 370         free_trackers_and_list(&arguments);
 371 }
 372
 373 void register_memory(int id)
 374 {
 375         my_id = id;
 376         add_merge_hook(my_id, &merge_func);
 377         add_hook(&match_function_def, FUNC_DEF_HOOK);
 378         add_hook(&match_declarations, DECLARATION_HOOK);
 379         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 380         add_hook(&match_condition, CONDITION_HOOK);
 381         add_hook(&match_assign, ASSIGNMENT_HOOK);
 382         add_hook(&match_return, RETURN_HOOK);
 383         add_hook(&match_end_func, END_FUNC_HOOK);
 384 }