check_free_strict.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  * check_memory() is getting too big and messy.
  20  *
  21  */
  22
  23 #include <string.h>
  24 #include "smatch.h"
  25 #include "smatch_slist.h"
  26 #include "smatch_extra.h"
  27
  28 static int my_id;
  29
  30 STATE(freed);
  31 STATE(ok);
  32
  33 static void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
  34 {
  35         if (sm->state != &ok)
  36                 set_state(my_id, sm->name, sm->sym, &ok);
  37 }
  38
  39 static void pre_merge_hook(struct sm_state *sm)
  40 {
  41         if (is_impossible_path())
  42                 set_state(my_id, sm->name, sm->sym, &ok);
  43 }
  44
  45 static int is_freed(struct expression *expr)
  46 {
  47         struct sm_state *sm;
  48
  49         sm = get_sm_state_expr(my_id, expr);
  50         if (sm && slist_has_state(sm->possible, &freed))
  51                 return 1;
  52         return 0;
  53 }
  54
  55 static void match_symbol(struct expression *expr)
  56 {
  57         struct expression *parent;
  58         char *name;
  59
  60         if (is_impossible_path())
  61                 return;
  62
  63         parent = expr_get_parent_expr(expr);
  64         while (parent && parent->type == EXPR_PREOP && parent->op == '(')
  65                 parent = expr_get_parent_expr(parent);
  66         if (parent && parent->type == EXPR_PREOP && parent->op == '&')
  67                 return;
  68
  69         if (!is_freed(expr))
  70                 return;
  71         name = expr_to_var(expr);
  72         sm_msg("warn: '%s' was already freed.", name);
  73         free_string(name);
  74 }
  75
  76 static void match_dereferences(struct expression *expr)
  77 {
  78         char *name;
  79
  80         if (expr->type != EXPR_PREOP)
  81                 return;
  82
  83         if (is_impossible_path())
  84                 return;
  85
  86         expr = strip_expr(expr->unop);
  87         if (!is_freed(expr))
  88                 return;
  89         name = expr_to_var(expr);
  90         sm_msg("error: dereferencing freed memory '%s'", name);
  91         set_state_expr(my_id, expr, &ok);
  92         free_string(name);
  93 }
  94
  95 static int ignored_params[16];
  96
  97 static void set_ignored_params(struct expression *call)
  98 {
  99         struct expression *arg;
 100         const char *p;
 101         int i;
 102
 103         memset(&ignored_params, 0, sizeof(ignored_params));
 104
 105         i = -1;
 106         FOR_EACH_PTR(call->args, arg) {
 107                 i++;
 108                 if (arg->type != EXPR_STRING)
 109                         continue;
 110                 goto found;
 111         } END_FOR_EACH_PTR(arg);
 112
 113         return;
 114
 115 found:
 116         i++;
 117         p = arg->string->data;
 118         while ((p = strchr(p, '%'))) {
 119                 if (i >= ARRAY_SIZE(ignored_params))
 120                         return;
 121                 p++;
 122                 if (*p == '%') {
 123                         p++;
 124                         continue;
 125                 }
 126                 if (*p == '.')
 127                         p++;
 128                 if (*p == '*')
 129                         i++;
 130                 if (*p == 'p')
 131                         ignored_params[i] = 1;
 132                 i++;
 133         }
 134 }
 135
 136 static int is_free_func(struct expression *fn)
 137 {
 138         char *name;
 139         int ret = 0;
 140
 141         name = expr_to_str(fn);
 142         if (!name)
 143                 return 0;
 144         if (strstr(name, "free"))
 145                 ret = 1;
 146         free_string(name);
 147
 148         return ret;
 149 }
 150
 151 static void match_call(struct expression *expr)
 152 {
 153         struct expression *arg;
 154         char *name;
 155         int i;
 156
 157         if (is_impossible_path())
 158                 return;
 159
 160         set_ignored_params(expr);
 161
 162         i = -1;
 163         FOR_EACH_PTR(expr->args, arg) {
 164                 i++;
 165                 if (!is_pointer(arg))
 166                         continue;
 167                 if (!is_freed(arg))
 168                         continue;
 169                 if (ignored_params[i])
 170                         continue;
 171
 172                 name = expr_to_var(arg);
 173                 if (is_free_func(expr->fn))
 174                         sm_msg("error: double free of '%s'", name);
 175                 else
 176                         sm_msg("warn: passing freed memory '%s'", name);
 177                 set_state_expr(my_id, arg, &ok);
 178                 free_string(name);
 179         } END_FOR_EACH_PTR(arg);
 180 }
 181
 182 static void match_return(struct expression *expr)
 183 {
 184         char *name;
 185
 186         if (is_impossible_path())
 187                 return;
 188
 189         if (!expr)
 190                 return;
 191         if (!is_freed(expr))
 192                 return;
 193
 194         name = expr_to_var(expr);
 195         sm_msg("warn: returning freed memory '%s'", name);
 196         set_state_expr(my_id, expr, &ok);
 197         free_string(name);
 198 }
 199
 200 static void match_free(const char *fn, struct expression *expr, void *param)
 201 {
 202         struct expression *arg;
 203
 204         if (is_impossible_path())
 205                 return;
 206
 207         arg = get_argument_from_call_expr(expr->args, PTR_INT(param));
 208         if (!arg)
 209                 return;
 210         if (is_freed(arg)) {
 211                 char *name = expr_to_var(arg);
 212
 213                 sm_msg("error: double free of '%s'", name);
 214                 free_string(name);
 215         }
 216         set_state_expr(my_id, arg, &freed);
 217 }
 218
 219 static void set_param_freed(struct expression *expr, int param, char *key, char *value)
 220 {
 221         struct expression *arg;
 222         char *name;
 223         struct symbol *sym;
 224         struct sm_state *sm;
 225
 226         while (expr->type == EXPR_ASSIGNMENT)
 227                 expr = strip_expr(expr->right);
 228         if (expr->type != EXPR_CALL)
 229                 return;
 230
 231         arg = get_argument_from_call_expr(expr->args, param);
 232         if (!arg)
 233                 return;
 234         name = get_variable_from_key(arg, key, &sym);
 235         if (!name || !sym)
 236                 goto free;
 237
 238         if (!is_impossible_path()) {
 239                 sm = get_sm_state(my_id, name, sym);
 240                 if (sm && slist_has_state(sm->possible, &freed)) {
 241                         sm_msg("warn: '%s' double freed", name);
 242                         set_state(my_id, name, sym, &ok);  /* fixme: doesn't silence anything.  I know */
 243                 }
 244         }
 245
 246         set_state(my_id, name, sym, &freed);
 247 free:
 248         free_string(name);
 249 }
 250
 251 int parent_is_free_var_sym_strict(const char *name, struct symbol *sym)
 252 {
 253         char buf[256];
 254         char *start;
 255         char *end;
 256         struct smatch_state *state;
 257
 258         strncpy(buf, name, sizeof(buf) - 1);
 259         buf[sizeof(buf) - 1] = '\0';
 260
 261         start = &buf[0];
 262         while ((*start == '&'))
 263                 start++;
 264
 265         while ((end = strrchr(start, '-'))) {
 266                 *end = '\0';
 267                 state = __get_state(my_id, start, sym);
 268                 if (state == &freed)
 269                         return 1;
 270         }
 271         return 0;
 272 }
 273
 274 int parent_is_free_strict(struct expression *expr)
 275 {
 276         struct symbol *sym;
 277         char *var;
 278         int ret = 0;
 279
 280         expr = strip_expr(expr);
 281         var = expr_to_var_sym(expr, &sym);
 282         if (!var || !sym)
 283                 goto free;
 284         ret = parent_is_free_var_sym_strict(var, sym);
 285 free:
 286         free_string(var);
 287         return ret;
 288 }
 289
 290 void check_free_strict(int id)
 291 {
 292         my_id = id;
 293
 294         if (option_project != PROJ_KERNEL)
 295                 return;
 296
 297         add_function_hook("kfree", &match_free, INT_PTR(0));
 298         add_function_hook("kmem_cache_free", &match_free, INT_PTR(1));
 299
 300         if (option_spammy)
 301                 add_hook(&match_symbol, SYM_HOOK);
 302         add_hook(&match_dereferences, DEREF_HOOK);
 303         add_hook(&match_call, FUNCTION_CALL_HOOK);
 304         add_hook(&match_return, RETURN_HOOK);
 305
 306         add_modification_hook_late(my_id, &ok_to_use);
 307         add_pre_merge_hook(my_id, &pre_merge_hook);
 308
 309         select_return_states_hook(PARAM_FREED, &set_param_freed);
 310 }