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(returned);
  20 STATE(unfree);
  21
  22 static const char *allocation_funcs[] = {
  23         "malloc",
  24         "kmalloc",
  25         NULL,
  26 };
  27
  28 static int is_allocation(struct expression *expr)
  29 {
  30         char *fn_name;
  31         int i;
  32
  33         if (expr->type != EXPR_CALL)
  34                 return 0;
  35
  36         if (!(fn_name = get_variable_from_expr(expr->fn, NULL)))
  37                 return 0;
  38
  39         for (i = 0; allocation_funcs[i]; i++) {
  40                 if (!strcmp(fn_name, allocation_funcs[i])) {
  41                         free_string(fn_name);
  42                         return 1;
  43                 }
  44         }
  45         free_string(fn_name);
  46         return 0;
  47 }
  48
  49 static int is_freed(const char *name, struct symbol *sym)
  50 {
  51         struct state_list *slist;
  52
  53         slist = get_possible_states(name, my_id, sym);
  54         if (slist_has_state(slist, &isfree)) {
  55                 return 1;
  56         }
  57         return 0;
  58 }
  59
  60 static void match_assign(struct expression *expr)
  61 {
  62         struct expression *left, *right;
  63         char *left_name, *right_name;
  64         struct symbol *left_sym, *right_sym;
  65         struct smatch_state *state;
  66
  67         left = strip_expr(expr->left);
  68         left_name = get_variable_from_expr(left, &left_sym);
  69         if (!left_name)
  70                 return;
  71         if (!left_sym) {
  72                 free_string(left_name);
  73                 return;
  74         }
  75
  76         right = strip_expr(expr->right);
  77         if (is_allocation(right) && !(left_sym->ctype.modifiers &
  78                         (MOD_NONLOCAL | MOD_STATIC | MOD_ADDRESSABLE))) {
  79                 set_state(left_name, my_id, left_sym, &allocated);
  80                 return;
  81         }
  82
  83         right_name = get_variable_from_expr(right, &right_sym);
  84         if (right_name && (state = get_state(right_name, my_id, right_sym))) {
  85                 if (state == &isfree)
  86                         smatch_msg("assigning freed pointer");
  87                 set_state(right_name, my_id, right_sym, &assigned);
  88         }
  89         free_string(right_name);
  90
  91         if (is_freed(left_name, left_sym)) {
  92                 set_state(left_name, my_id, left_sym, &unfree);
  93         }
  94 }
  95
  96 static int is_null(char *name, struct symbol *sym)
  97 {
  98         struct smatch_state *state;
  99
 100         /*
 101          * FIXME.  Ha ha ha... This is so wrong.
 102          * I'm pulling in data from the check_null_deref script.
 103          * I just happen to know that its ID is 3.
 104          * The correct approved way to do this is to get the data from
 105          * smatch_extra.  But right now smatch_extra doesn't track it.
 106          */
 107         state = get_state(name, 3, sym);
 108         if (state && !strcmp(state->name, "isnull"))
 109                 return 1;
 110         return 0;
 111 }
 112
 113 static void match_kfree(struct expression *expr)
 114 {
 115         struct expression *ptr_expr;
 116         char *fn_name;
 117         char *ptr_name;
 118         struct symbol *ptr_sym;
 119
 120
 121         fn_name = get_variable_from_expr(expr->fn, NULL);
 122
 123         if (!fn_name || strcmp(fn_name, "kfree"))
 124                 return;
 125
 126         ptr_expr = get_argument_from_call_expr(expr->args, 0);
 127         ptr_name = get_variable_from_expr(ptr_expr, &ptr_sym);
 128         if (is_freed(ptr_name, ptr_sym) && !is_null(ptr_name, ptr_sym)) {
 129                 smatch_msg("double free of %s", ptr_name);
 130         }
 131         set_state(ptr_name, my_id, ptr_sym, &isfree);
 132
 133         free_string(fn_name);
 134 }
 135
 136 static int possibly_allocated(struct state_list *slist)
 137 {
 138         struct sm_state *tmp;
 139
 140         FOR_EACH_PTR(slist, tmp) {
 141                 if (tmp->state == &allocated)
 142                         return 1;
 143         } END_FOR_EACH_PTR(tmp);
 144         return 0;
 145 }
 146
 147 static void check_for_allocated()
 148 {
 149         struct state_list *slist;
 150         struct sm_state *tmp;
 151
 152         return;
 153
 154         slist = get_all_states(my_id);
 155         FOR_EACH_PTR(slist, tmp) {
 156                 if (possibly_allocated(tmp->possible) &&
 157                         !is_null(tmp->name, tmp->sym))
 158                         smatch_msg("possible memery leak of %s", tmp->name);
 159         } END_FOR_EACH_PTR(tmp);
 160
 161 }
 162
 163 static void match_return(struct statement *stmt)
 164 {
 165         char *name;
 166         struct symbol *sym;
 167         struct smatch_state *state;
 168
 169         name = get_variable_from_expr(stmt->ret_value, &sym);
 170         if ((state = get_state(name, my_id, sym))) {
 171                 set_state(name, my_id, sym, &returned);
 172         }
 173
 174         check_for_allocated();
 175 }
 176
 177 static void match_function_call(struct expression *expr)
 178 {
 179
 180
 181 }
 182
 183
 184 static void match_end_func(struct symbol *sym)
 185 {
 186         check_for_allocated();
 187 }
 188
 189 void register_memory(int id)
 190 {
 191         my_id = id;
 192         add_hook(&match_kfree, FUNCTION_CALL_HOOK);
 193         add_hook(&match_assign, ASSIGNMENT_HOOK);
 194         add_hook(&match_return, RETURN_HOOK);
 195         add_hook(&match_end_func, END_FUNC_HOOK);
 196 }