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 static struct tracker_list *arguments;
  32
  33 static const char *allocation_funcs[] = {
  34         "malloc",
  35         "kmalloc",
  36         "kzalloc",
  37         NULL,
  38 };
  39
  40 static struct smatch_state *merge_func(const char *name, struct symbol *sym,
  41                                        struct smatch_state *s1,
  42                                        struct smatch_state *s2)
  43 {
  44         if (!strcmp(name, "-"))
  45                 return &assigned;
  46         /* this is normal merge */
  47         if (!s1 || !s2)
  48                 return &undefined;
  49         return &merged;
  50 }
  51
  52 static void assign_parent(struct symbol *sym)
  53 {
  54         set_state("-", my_id, sym, &assigned);
  55 }
  56
  57 static int parent_is_assigned(struct symbol *sym)
  58 {
  59         struct smatch_state *state;
  60
  61         state = get_state("-", my_id, sym);
  62         if (state == &assigned)
  63                 return 1;
  64         return 0;
  65 }
  66
  67 static int is_allocation(struct expression *expr)
  68 {
  69         char *fn_name;
  70         int i;
  71
  72         if (expr->type != EXPR_CALL)
  73                 return 0;
  74
  75         if (!(fn_name = get_variable_from_expr(expr->fn, NULL)))
  76                 return 0;
  77
  78         for (i = 0; allocation_funcs[i]; i++) {
  79                 if (!strcmp(fn_name, allocation_funcs[i])) {
  80                         free_string(fn_name);
  81                         return 1;
  82                 }
  83         }
  84         free_string(fn_name);
  85         return 0;
  86 }
  87
  88 static int is_freed(const char *name, struct symbol *sym)
  89 {
  90         struct state_list *slist;
  91
  92         slist = get_possible_states(name, my_id, sym);
  93         if (slist_has_state(slist, &isfree)) {
  94                 return 1;
  95         }
  96         return 0;
  97 }
  98
  99 static int is_argument(struct symbol *sym)
 100 {
 101         struct tracker *arg;
 102
 103         FOR_EACH_PTR(arguments, arg) {
 104                 if (arg->sym == sym)
 105                         return 1;
 106         } END_FOR_EACH_PTR(arg);
 107         return 0;
 108 }
 109
 110 static void match_function_def(struct symbol *sym)
 111 {
 112         struct symbol *arg;
 113
 114         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 115                 add_tracker(&arguments, (arg->ident?arg->ident->name:"NULL"), my_id, arg);
 116         } END_FOR_EACH_PTR(arg);
 117 }
 118
 119 static void match_declarations(struct symbol *sym)
 120 {
 121         const char *name;
 122
 123         if ((get_base_type(sym))->type == SYM_ARRAY) {
 124                 return;
 125         }
 126
 127         name = sym->ident->name;
 128
 129         if (sym->initializer) {
 130                 if (is_allocation(sym->initializer)) {
 131                         set_state(name, my_id, sym, &malloced);
 132                 } else {
 133                         assign_parent(sym);
 134                 }
 135         }
 136 }
 137
 138 static int is_parent(struct expression *expr)
 139 {
 140         if (expr->type == EXPR_DEREF)
 141                 return 0;
 142         return 1;
 143 }
 144
 145 static int assign_seen;
 146 static int handle_double_assign(struct expression *expr)
 147 {
 148         struct symbol *sym;
 149         char *name;
 150
 151         if (expr->right->type != EXPR_ASSIGNMENT)
 152                 return 0;
 153         assign_seen++;
 154
 155         name = get_variable_from_expr_complex(expr->left, &sym);
 156         if (name && is_parent(expr->left))
 157                 assign_parent(sym);
 158
 159         name = get_variable_from_expr_complex(expr->right->left, &sym);
 160         if (name && is_parent(expr->right->left))
 161                 assign_parent(sym);
 162
 163         name = get_variable_from_expr_complex(expr->right->right, &sym);
 164         if (name && is_parent(expr->right->right))
 165                 assign_parent(sym);
 166
 167         return 1;
 168 }
 169
 170 static void match_assign(struct expression *expr)
 171 {
 172         struct expression *left, *right;
 173         char *left_name = NULL;
 174         char *right_name = NULL;
 175         struct symbol *left_sym, *right_sym;
 176         struct smatch_state *state;
 177
 178         if (assign_seen) {
 179                 assign_seen--;
 180                 return;
 181         }
 182
 183         if (handle_double_assign(expr)) {
 184                 return;
 185         }
 186
 187         left = strip_expr(expr->left);
 188         left_name = get_variable_from_expr_complex(left, &left_sym);
 189
 190         right = strip_expr(expr->right);
 191         if (left_name && left_sym && is_allocation(right) &&
 192             !(left_sym->ctype.modifiers &
 193               (MOD_NONLOCAL | MOD_STATIC | MOD_ADDRESSABLE)) &&
 194             !parent_is_assigned(left_sym)) {
 195                 set_state(left_name, my_id, left_sym, &malloced);
 196                 goto exit;
 197         }
 198
 199         right_name = get_variable_from_expr_complex(right, &right_sym);
 200
 201         if (right_name && (state = get_state(right_name, my_id, right_sym))) {
 202                 if (state == &isfree)
 203                         smatch_msg("error: assigning freed pointer");
 204                 set_state(right_name, my_id, right_sym, &assigned);
 205         }
 206
 207         if (is_freed(left_name, left_sym)) {
 208                 set_state(left_name, my_id, left_sym, &unfree);
 209         }
 210         if (left_name && is_parent(left))
 211                 assign_parent(left_sym);
 212         if (right_name && is_parent(right))
 213                 assign_parent(right_sym);
 214 exit:
 215         free_string(left_name);
 216         free_string(right_name);
 217 }
 218
 219 static int is_null(char *name, struct symbol *sym)
 220 {
 221         struct smatch_state *state;
 222
 223         /*
 224          * FIXME.  Ha ha ha... This is so wrong.
 225          * I'm pulling in data from the check_null_deref script.
 226          * I just happen to know that its ID is 3.
 227          * The correct approved way to do this is to get the data from
 228          * smatch_extra.  But right now smatch_extra doesn't track it.
 229          */
 230         state = get_state(name, my_id, sym);
 231         if (state && !strcmp(state->name, "isnull"))
 232                 return 1;
 233         return 0;
 234 }
 235
 236 static void match_kfree(struct expression *expr)
 237 {
 238         struct expression *ptr_expr;
 239         char *ptr_name;
 240         struct symbol *ptr_sym;
 241
 242         ptr_expr = get_argument_from_call_expr(expr->args, 0);
 243         ptr_name = get_variable_from_expr_complex(ptr_expr, &ptr_sym);
 244         if (is_freed(ptr_name, ptr_sym) && !is_null(ptr_name, ptr_sym)) {
 245                 smatch_msg("error: double free of %s", ptr_name);
 246         }
 247         set_state(ptr_name, my_id, ptr_sym, &isfree);
 248         free_string(ptr_name);
 249 }
 250
 251 static int possibly_allocated(struct state_list *slist)
 252 {
 253         struct sm_state *tmp;
 254
 255         FOR_EACH_PTR(slist, tmp) {
 256                 if (tmp->state == &allocated)
 257                         return 1;
 258                 if (tmp->state == &malloced)
 259                         return 1;
 260         } END_FOR_EACH_PTR(tmp);
 261         return 0;
 262 }
 263
 264 static void check_for_allocated()
 265 {
 266         struct state_list *slist;
 267         struct sm_state *tmp;
 268
 269         slist = get_all_states(my_id);
 270         FOR_EACH_PTR(slist, tmp) {
 271                 if (possibly_allocated(tmp->possible) &&
 272                     !is_null(tmp->name, tmp->sym) &&
 273                     !is_argument(tmp->sym) &&
 274                     !parent_is_assigned(tmp->sym))
 275                         smatch_msg("error: memery leak of %s", tmp->name);
 276         } END_FOR_EACH_PTR(tmp);
 277         free_slist(&slist);
 278 }
 279
 280 static void match_return(struct statement *stmt)
 281 {
 282         char *name;
 283         struct symbol *sym;
 284
 285         name = get_variable_from_expr_complex(stmt->ret_value, &sym);
 286         if (sym)
 287                 assign_parent(sym);
 288         free_string(name);
 289         check_for_allocated();
 290 }
 291
 292 static void set_new_true_false_paths(const char *name, struct symbol *sym)
 293 {
 294         struct smatch_state *tmp;
 295
 296         tmp = get_state(name, my_id, sym);
 297
 298         if (!tmp) {
 299                 return;
 300         }
 301
 302         if (tmp == &isfree) {
 303                 smatch_msg("warn: why do you care about freed memory?");
 304         }
 305
 306         if (tmp == &assigned) {
 307                 /* we don't care about assigned pointers any more */
 308                 return;
 309         }
 310         set_true_false_states(name, my_id, sym, &allocated, &isnull);
 311 }
 312
 313 static void match_condition(struct expression *expr)
 314 {
 315         struct symbol *sym;
 316         char *name;
 317
 318         expr = strip_expr(expr);
 319         switch(expr->type) {
 320         case EXPR_PREOP:
 321         case EXPR_SYMBOL:
 322         case EXPR_DEREF:
 323                 name = get_variable_from_expr_complex(expr, &sym);
 324                 if (!name)
 325                         return;
 326                 set_new_true_false_paths(name, sym);
 327                 free_string(name);
 328                 return;
 329         case EXPR_ASSIGNMENT:
 330                 assign_seen++;
 331                  /* You have to deal with stuff like if (a = b = c) */
 332                 match_condition(expr->right);
 333                 match_condition(expr->left);
 334                 return;
 335         default:
 336                 return;
 337         }
 338 }
 339
 340 static void match_function_call(struct expression *expr)
 341 {
 342         struct expression *tmp;
 343         struct symbol *sym;
 344         char *name;
 345         char *fn_name;
 346         struct sm_state *state;
 347
 348         fn_name = get_variable_from_expr(expr->fn, NULL);
 349
 350         if (fn_name && !strcmp(fn_name, "kfree")) {
 351                 match_kfree(expr);
 352         }
 353
 354         FOR_EACH_PTR(expr->args, tmp) {
 355                 tmp = strip_expr(tmp);
 356                 name = get_variable_from_expr_complex(tmp, &sym);
 357                 if (!name)
 358                         continue;
 359                 if ((state = get_sm_state(name, my_id, sym))) {
 360                         if (possibly_allocated(state->possible)) {
 361                                 set_state(name, my_id, sym, &assigned);
 362                         }
 363                 }
 364                 assign_parent(sym);
 365         } END_FOR_EACH_PTR(tmp);
 366 }
 367
 368 static void match_end_func(struct symbol *sym)
 369 {
 370         check_for_allocated();
 371         free_trackers_and_list(&arguments);
 372 }
 373
 374 void register_memory(int id)
 375 {
 376         my_id = id;
 377         add_merge_hook(my_id, &merge_func);
 378         add_hook(&match_function_def, FUNC_DEF_HOOK);
 379         add_hook(&match_declarations, DECLARATION_HOOK);
 380         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 381         add_hook(&match_condition, CONDITION_HOOK);
 382         add_hook(&match_assign, ASSIGNMENT_HOOK);
 383         add_hook(&match_return, RETURN_HOOK);
 384         add_hook(&match_end_func, END_FUNC_HOOK);
 385 }