check_free.c

   1 /*
   2  * sparse/check_free.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * check_memory() is getting too big and messy.
  12  *
  13  */
  14
  15 #include "smatch.h"
  16 #include "smatch_slist.h"
  17
  18 static int my_id;
  19
  20 STATE(freed);
  21 STATE(ok);
  22
  23 static void ok_to_use(struct sm_state *sm)
  24 {
  25         if (sm->state != &ok)
  26                 set_state(my_id, sm->name, sm->sym, &ok);
  27 }
  28
  29 static int is_freed(struct expression *expr)
  30 {
  31         struct sm_state *sm;
  32
  33         sm = get_sm_state_expr(my_id, expr);
  34         if (sm && slist_has_state(sm->possible, &freed))
  35                 return 1;
  36         return 0;
  37 }
  38
  39 static void match_symbol(struct expression *expr)
  40 {
  41         char *name;
  42
  43         if (!is_freed(expr))
  44                 return;
  45         name = get_variable_from_expr(expr, NULL);
  46         sm_msg("warn: '%s' was already freed.", name);
  47         free_string(name);
  48 }
  49
  50 static void match_dereferences(struct expression *expr)
  51 {
  52         char *name;
  53
  54         if (expr->type != EXPR_PREOP)
  55                 return;
  56         expr = strip_expr(expr->unop);
  57
  58         if (!is_freed(expr))
  59                 return;
  60         name = get_variable_from_expr(expr, NULL);
  61         sm_msg("error: dereferencing freed memory '%s'", name);
  62         set_state_expr(my_id, expr, &ok);
  63         free_string(name);
  64 }
  65
  66 static void match_free(const char *fn, struct expression *expr, void *param)
  67 {
  68         struct expression *arg;
  69
  70         arg = get_argument_from_call_expr(expr->args, PTR_INT(param));
  71         if (!arg)
  72                 return;
  73         /* option_spammy already prints a warning here */
  74         if (!option_spammy && is_freed(arg)) {
  75                 char *name = get_variable_from_expr(arg, NULL);
  76
  77                 sm_msg("error: double free of '%s'", name);
  78                 free_string(name);
  79         }
  80         set_state_expr(my_id, arg, &freed);
  81 }
  82
  83 void check_free(int id)
  84 {
  85         my_id = id;
  86
  87         if (option_project == PROJ_KERNEL)
  88                 add_function_hook("kfree", &match_free, (void *)0);
  89         else
  90                 add_function_hook("free", &match_free, (void *)0);
  91
  92         if (option_spammy)
  93                 add_hook(&match_symbol, SYM_HOOK);
  94         else
  95                 add_hook(&match_dereferences, DEREF_HOOK);
  96
  97         add_modification_hook(my_id, &ok_to_use);
  98 }