check_free.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
  27 static int my_id;
  28
  29 STATE(freed);
  30 STATE(ok);
  31
  32 static void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
  33 {
  34         if (sm->state != &ok)
  35                 set_state(my_id, sm->name, sm->sym, &ok);
  36 }
  37
  38 static int is_freed(struct expression *expr)
  39 {
  40         struct sm_state *sm;
  41
  42         sm = get_sm_state_expr(my_id, expr);
  43         if (sm && slist_has_state(sm->possible, &freed))
  44                 return 1;
  45         return 0;
  46 }
  47
  48 static void match_symbol(struct expression *expr)
  49 {
  50         char *name;
  51
  52         if (!is_freed(expr))
  53                 return;
  54         name = expr_to_var(expr);
  55         sm_msg("warn: '%s' was already freed.", name);
  56         free_string(name);
  57 }
  58
  59 static void match_dereferences(struct expression *expr)
  60 {
  61         char *name;
  62
  63         if (expr->type != EXPR_PREOP)
  64                 return;
  65         expr = strip_expr(expr->unop);
  66
  67         if (!is_freed(expr))
  68                 return;
  69         name = expr_to_var(expr);
  70         sm_msg("error: dereferencing freed memory '%s'", name);
  71         set_state_expr(my_id, expr, &ok);
  72         free_string(name);
  73 }
  74
  75 static int ignored_params[16];
  76
  77 static void set_ignored_params(struct expression *call)
  78 {
  79         struct expression *arg;
  80         const char *p;
  81         int i;
  82
  83         memset(&ignored_params, 0, sizeof(ignored_params));
  84
  85         i = -1;
  86         FOR_EACH_PTR(call->args, arg) {
  87                 i++;
  88                 if (arg->type != EXPR_STRING)
  89                         continue;
  90                 goto found;
  91         } END_FOR_EACH_PTR(arg);
  92
  93         return;
  94
  95 found:
  96         i++;
  97         p = arg->string->data;
  98         while ((p = strchr(p, '%'))) {
  99                 if (i >= ARRAY_SIZE(ignored_params))
 100                         return;
 101                 p++;
 102                 if (*p == '%') {
 103                         p++;
 104                         continue;
 105                 }
 106                 if (*p == '.')
 107                         p++;
 108                 if (*p == '*')
 109                         i++;
 110                 if (*p == 'p')
 111                         ignored_params[i] = 1;
 112                 i++;
 113         }
 114 }
 115
 116 static int is_free_func(struct expression *fn)
 117 {
 118         char *name;
 119         int ret = 0;
 120
 121         name = expr_to_str(fn);
 122         if (!name)
 123                 return 0;
 124         if (strstr(name, "free"))
 125                 ret = 1;
 126         free_string(name);
 127
 128         return ret;
 129 }
 130
 131 static void match_call(struct expression *expr)
 132 {
 133         struct expression *arg;
 134         char *name;
 135         int i;
 136
 137         set_ignored_params(expr);
 138
 139         i = -1;
 140         FOR_EACH_PTR(expr->args, arg) {
 141                 i++;
 142                 if (!is_pointer(arg))
 143                         continue;
 144                 if (!is_freed(arg))
 145                         continue;
 146                 if (ignored_params[i])
 147                         continue;
 148
 149                 name = expr_to_var(arg);
 150                 if (is_free_func(expr->fn))
 151                         sm_msg("error: double free of '%s'", name);
 152                 else
 153                         sm_msg("warn: passing freed memory '%s'", name);
 154                 set_state_expr(my_id, arg, &ok);
 155                 free_string(name);
 156         } END_FOR_EACH_PTR(arg);
 157 }
 158
 159 static void match_return(struct expression *expr)
 160 {
 161         char *name;
 162
 163         if (!expr)
 164                 return;
 165         if (!is_freed(expr))
 166                 return;
 167
 168         name = expr_to_var(expr);
 169         sm_msg("warn: returning freed memory '%s'", name);
 170         set_state_expr(my_id, expr, &ok);
 171         free_string(name);
 172 }
 173
 174 static void match_free(const char *fn, struct expression *expr, void *param)
 175 {
 176         struct expression *arg;
 177
 178         arg = get_argument_from_call_expr(expr->args, PTR_INT(param));
 179         if (!arg)
 180                 return;
 181         if (is_freed(arg)) {
 182                 char *name = expr_to_var(arg);
 183
 184                 sm_msg("error: double free of '%s'", name);
 185                 free_string(name);
 186         }
 187         set_state_expr(my_id, arg, &freed);
 188 }
 189
 190 static void set_param_freed(struct expression *arg, char *key, char *unused)
 191 {
 192         struct symbol *sym;
 193         char *name;
 194
 195         name = get_variable_from_key(arg, key, &sym);
 196         if (!name || !sym)
 197                 goto free;
 198
 199         set_state(my_id, name, sym, &freed);
 200 free:
 201         free_string(name);
 202 }
 203
 204 int parent_is_free_var_sym(const char *name, struct symbol *sym)
 205 {
 206         char buf[256];
 207         char *start;
 208         char *end;
 209         struct smatch_state *state;
 210
 211         strncpy(buf, name, sizeof(buf) - 1);
 212         buf[sizeof(buf) - 1] = '\0';
 213
 214         start = &buf[0];
 215         while ((*start == '&'))
 216                 start++;
 217
 218         while ((end = strrchr(start, '-'))) {
 219                 *end = '\0';
 220                 state = get_state(my_id, start, sym);
 221                 if (state == &freed)
 222                         return 1;
 223         }
 224         return 0;
 225 }
 226
 227 int parent_is_free(struct expression *expr)
 228 {
 229         struct symbol *sym;
 230         char *var;
 231         int ret = 0;
 232
 233         expr = strip_expr(expr);
 234         var = expr_to_var_sym(expr, &sym);
 235         if (!var || !sym)
 236                 goto free;
 237         ret = parent_is_free_var_sym(var, sym);
 238 free:
 239         free_string(var);
 240         return ret;
 241 }
 242
 243 void check_free(int id)
 244 {
 245         my_id = id;
 246
 247         if (option_project == PROJ_KERNEL) {
 248                 add_function_hook("kfree", &match_free, INT_PTR(0));
 249                 add_function_hook("kmem_cache_free", &match_free, INT_PTR(1));
 250         } else {
 251                 add_function_hook("free", &match_free, INT_PTR(0));
 252         }
 253
 254         if (option_spammy)
 255                 add_hook(&match_symbol, SYM_HOOK);
 256         add_hook(&match_dereferences, DEREF_HOOK);
 257         add_hook(&match_call, FUNCTION_CALL_HOOK);
 258         add_hook(&match_return, RETURN_HOOK);
 259
 260         add_modification_hook(my_id, &ok_to_use);
 261         select_call_implies_hook(PARAM_FREED, &set_param_freed);
 262 }