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 array_check(struct expression *expr)
  34 {
  35         struct expression *array_expr;
  36         int array_size;
  37         struct expression *offset;
  38         struct range_list *rl;
  39
  40         expr = strip_expr(expr);
  41         if (!is_array(expr))
  42                 return;
  43
  44         array_expr = get_array_base(expr);
  45         array_size = get_array_size(array_expr);
  46         if (!array_size || array_size == 1)
  47                 return;
  48
  49         offset = get_array_offset(expr);
  50         get_absolute_rl(offset, &rl);
  51         if (rl_max(rl).uvalue < array_size)
  52                 return;
  53         if (buf_comparison_index_ok(expr))
  54                 return;
  55
  56         if (getting_address(expr))
  57                 return;
  58         if (is_capped(offset))
  59                 return;
  60         set_state_expr(my_used_id, offset, alloc_state_num(array_size));
  61 }
  62
  63 static void match_condition(struct expression *expr)
  64 {
  65         int left;
  66         sval_t sval;
  67         struct state_list *slist;
  68         struct sm_state *tmp;
  69         int boundary;
  70
  71         if (!expr || expr->type != EXPR_COMPARE)
  72                 return;
  73         if (get_macro_name(expr->pos))
  74                 return;
  75         if (get_implied_value(expr->left, &sval))
  76                 left = 1;
  77         else if (get_implied_value(expr->right, &sval))
  78                 left = 0;
  79         else
  80                 return;
  81
  82         if (left)
  83                 slist = get_possible_states_expr(my_used_id, expr->right);
  84         else
  85                 slist = get_possible_states_expr(my_used_id, expr->left);
  86         if (!slist)
  87                 return;
  88         FOR_EACH_PTR(slist, tmp) {
  89                 if (tmp->state == &merged || tmp->state == &undefined)
  90                         continue;
  91                 boundary = PTR_INT(tmp->state->data);
  92                 boundary -= sval.value;
  93                 if (boundary < 1 && boundary > -1) {
  94                         char *name;
  95
  96                         name = expr_to_var(left ? expr->right : expr->left);
  97                         sm_error("testing array offset '%s' after use.", name);
  98                         return;
  99                 }
 100         } END_FOR_EACH_PTR(tmp);
 101 }
 102
 103 void check_testing_index_after_use(int id)
 104 {
 105         my_used_id = id;
 106         set_dynamic_states(my_used_id);
 107         add_hook(&array_check, OP_HOOK);
 108         add_hook(&match_condition, CONDITION_HOOK);
 109         add_modification_hook(my_used_id, &set_undefined);
 110 }