check_testing_index_after_use.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 #include <stdlib.h>
  19 #include "parse.h"
  20 #include "smatch.h"
  21 #include "smatch_slist.h"
  22 #include "smatch_extra.h"
  23
  24 /*
  25  * This check has two smatch IDs.
  26  * my_used_id - keeps a record of array offsets that have been used.
  27  *              If the code checks that they are within bounds later on,
  28  *              we complain about using an array offset before checking
  29  *              that it is within bounds.
  30  */
  31 static int my_used_id;
  32
  33 static void delete(struct sm_state *sm, struct expression *mod_expr)
  34 {
  35         set_state(my_used_id, sm->name, sm->sym, &undefined);
  36 }
  37
  38 static void array_check(struct expression *expr)
  39 {
  40         struct expression *array_expr;
  41         int array_size;
  42         struct expression *offset;
  43         struct range_list *rl;
  44
  45         expr = strip_expr(expr);
  46         if (!is_array(expr))
  47                 return;
  48
  49         array_expr = get_array_base(expr);
  50         array_size = get_array_size(array_expr);
  51         if (!array_size || array_size == 1)
  52                 return;
  53
  54         offset = get_array_offset(expr);
  55         get_absolute_rl(offset, &rl);
  56         if (rl_max(rl).uvalue < array_size)
  57                 return;
  58         if (buf_comparison_index_ok(expr))
  59                 return;
  60
  61         if (getting_address())
  62                 return;
  63         if (is_capped(offset))
  64                 return;
  65         set_state_expr(my_used_id, offset, alloc_state_num(array_size));
  66 }
  67
  68 static void match_condition(struct expression *expr)
  69 {
  70         int left;
  71         sval_t sval;
  72         struct state_list *slist;
  73         struct sm_state *tmp;
  74         int boundary;
  75
  76         if (!expr || expr->type != EXPR_COMPARE)
  77                 return;
  78         if (get_macro_name(expr->pos))
  79                 return;
  80         if (get_implied_value(expr->left, &sval))
  81                 left = 1;
  82         else if (get_implied_value(expr->right, &sval))
  83                 left = 0;
  84         else
  85                 return;
  86
  87         if (left)
  88                 slist = get_possible_states_expr(my_used_id, expr->right);
  89         else
  90                 slist = get_possible_states_expr(my_used_id, expr->left);
  91         if (!slist)
  92                 return;
  93         FOR_EACH_PTR(slist, tmp) {
  94                 if (tmp->state == &merged || tmp->state == &undefined)
  95                         continue;
  96                 boundary = PTR_INT(tmp->state->data);
  97                 boundary -= sval.value;
  98                 if (boundary < 1 && boundary > -1) {
  99                         char *name;
 100
 101                         name = expr_to_var(left ? expr->right : expr->left);
 102                         sm_error("testing array offset '%s' after use.", name);
 103                         return;
 104                 }
 105         } END_FOR_EACH_PTR(tmp);
 106 }
 107
 108 void check_testing_index_after_use(int id)
 109 {
 110         my_used_id = id;
 111         set_dynamic_states(my_used_id);
 112         add_hook(&array_check, OP_HOOK);
 113         add_hook(&match_condition, CONDITION_HOOK);
 114         add_modification_hook(my_used_id, &delete);
 115 }