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check_get_user_overflow.c
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check_get_user_overflow.c
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/*
* Copyright (C) 2010 Dan Carpenter.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
*/
/*
* Looks for integers that we get from the user which can be attacked
* with an integer overflow.
*
*/
#include "smatch.h"
#include "smatch_slist.h"
static int my_max_id;
static int my_min_id;
STATE(capped);
STATE(user_data);
static void match_condition(struct expression *expr)
{
struct smatch_state *left_max_true = NULL;
struct smatch_state *left_max_false = NULL;
struct smatch_state *right_max_true = NULL;
struct smatch_state *right_max_false = NULL;
struct smatch_state *left_min_true = NULL;
struct smatch_state *left_min_false = NULL;
struct smatch_state *right_min_true = NULL;
struct smatch_state *right_min_false = NULL;
switch (expr->op) {
case '<':
case SPECIAL_LTE:
case SPECIAL_UNSIGNED_LT:
case SPECIAL_UNSIGNED_LTE:
left_max_true = &capped;
right_max_false = &capped;
right_min_true = &capped;
left_min_false = &capped;
break;
case '>':
case SPECIAL_GTE:
case SPECIAL_UNSIGNED_GT:
case SPECIAL_UNSIGNED_GTE:
left_max_false = &capped;
right_max_true = &capped;
left_min_true = &capped;
right_min_false = &capped;
break;
case SPECIAL_EQUAL:
left_max_true = &capped;
right_max_true = &capped;
left_min_true = &capped;
right_min_true = &capped;
break;
case SPECIAL_NOTEQUAL:
left_max_false = &capped;
right_max_false = &capped;
left_min_false = &capped;
right_min_false = &capped;
break;
default:
return;
}
if (get_state_expr(my_max_id, expr->left)) {
set_true_false_states_expr(my_max_id, expr->left, left_max_true, left_max_false);
set_true_false_states_expr(my_min_id, expr->left, left_min_true, left_min_false);
}
if (get_state_expr(my_max_id, expr->right)) {
set_true_false_states_expr(my_max_id, expr->right, right_max_true, right_max_false);
set_true_false_states_expr(my_min_id, expr->right, right_min_true, right_min_false);
}
}
static void match_normal_assign(struct expression *expr)
{
if (get_state_expr(my_max_id, expr->left)) {
set_state_expr(my_max_id, expr->left, &capped);
set_state_expr(my_min_id, expr->left, &capped);
}
}
static void match_assign(struct expression *expr)
{
char *name;
name = get_macro_name(expr->pos);
if (!name || strcmp(name, "get_user") != 0) {
match_normal_assign(expr);
return;
}
name = expr_to_var(expr->right);
if (!name || strcmp(name, "__val_gu") != 0)
goto free;
set_state_expr(my_max_id, expr->left, &user_data);
set_state_expr(my_min_id, expr->left, &user_data);
free:
free_string(name);
}
static void check_expr(struct expression *expr)
{
struct sm_state *sm;
sval_t max;
sval_t sval;
char *name;
int overflow = 0;
int underflow = 0;
sm = get_sm_state_expr(my_max_id, expr);
if (sm && slist_has_state(sm->possible, &user_data)) {
if (!get_absolute_max(expr, &max) || sval_cmp_val(max, 20000) > 0)
overflow = 1;
}
sm = get_sm_state_expr(my_min_id, expr);
if (sm && slist_has_state(sm->possible, &user_data)) {
if (!get_absolute_min(expr, &sval) ||
(sval_is_negative(sval) && sval_cmp_val(sval, -20000) < 0))
underflow = 1;
}
if (!overflow && !underflow)
return;
name = expr_to_var_sym(expr, NULL);
if (overflow && underflow)
sm_msg("warn: check for integer over/underflow '%s'", name);
else if (underflow)
sm_msg("warn: check for integer underflow '%s'", name);
else
sm_msg("warn: check for integer overflow '%s'", name);
free_string(name);
set_state_expr(my_max_id, expr, &capped);
set_state_expr(my_min_id, expr, &capped);
}
static void match_binop(struct expression *expr)
{
if (expr->op == '^')
return;
if (expr->op == '&')
return;
if (expr->op == '|')
return;
if (expr->op == SPECIAL_RIGHTSHIFT)
return;
if (expr->op == SPECIAL_LEFTSHIFT)
return;
check_expr(expr->left);
check_expr(expr->right);
}
void check_get_user_overflow(int id)
{
if (option_project != PROJ_KERNEL)
return;
my_max_id = id;
add_hook(&match_condition, CONDITION_HOOK);
add_hook(&match_assign, ASSIGNMENT_HOOK);
add_hook(&match_binop, BINOP_HOOK);
}
void check_get_user_overflow2(int id)
{
my_min_id = id;
}