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Avoid signed integer overflows in numeric conversions.

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Reported by Miroslav Lichvar <mlichvar@redhat.com>
in <https://lists.gnu.org/archive/html/guile-devel/2016-02/msg00045.html>

* libguile/conv-integer.i.c: Avoid signed overflow.
* libguile/numbers.c (scm_is_signed_integer): Avoid signed overflow.
This commit is contained in:
Mark H Weaver 2016-02-24 02:17:43 -05:00 • committed by Andy Wingo
parent 36321a8ffd
commit a8d1c7d610
2 changed files with 20 additions and 10 deletions
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15
libguile/conv-integer.i.c
View file

@ -64,25 +64,30 @@ SCM_TO_TYPE_PROTO (SCM val)
}
else
{
scm_t_intmax n;
scm_t_uintmax abs_n;
TYPE n;
size_t count;
if (mpz_sizeinbase (SCM_I_BIG_MPZ (val), 2)
> CHAR_BIT*sizeof (scm_t_uintmax))
goto out_of_range;
mpz_export (&n, &count, 1, sizeof (scm_t_uintmax), 0, 0,
mpz_export (&abs_n, &count, 1, sizeof (scm_t_uintmax), 0, 0,
SCM_I_BIG_MPZ (val));
if (mpz_sgn (SCM_I_BIG_MPZ (val)) >= 0)
{
if (n < 0)
if (abs_n <= TYPE_MAX)
n = abs_n;
else
goto out_of_range;
}
else
{
n = -n;
if (n >= 0)
/* Carefully avoid signed integer overflow. */
if (TYPE_MIN < 0 && abs_n - 1 <= -(TYPE_MIN + 1))
n = -1 - (TYPE)(abs_n - 1);
else
goto out_of_range;
}

15
libguile/numbers.c
View file

@ -1,4 +1,4 @@
/* Copyright (C) 1995-2015 Free Software Foundation, Inc.
/* Copyright (C) 1995-2016 Free Software Foundation, Inc.
*
* Portions Copyright 1990, 1991, 1992, 1993 by AT&T Bell Laboratories
* and Bellcore. See scm_divide.
@ -9641,6 +9641,7 @@ scm_is_signed_integer (SCM val, scm_t_intmax min, scm_t_intmax max)
}
else
{
scm_t_uintmax abs_n;
scm_t_intmax n;
size_t count;
@ -9648,18 +9649,22 @@ scm_is_signed_integer (SCM val, scm_t_intmax min, scm_t_intmax max)
> CHAR_BIT*sizeof (scm_t_uintmax))
return 0;
mpz_export (&n, &count, 1, sizeof (scm_t_uintmax), 0, 0,
mpz_export (&abs_n, &count, 1, sizeof (scm_t_uintmax), 0, 0,
SCM_I_BIG_MPZ (val));
if (mpz_sgn (SCM_I_BIG_MPZ (val)) >= 0)
{
if (n < 0)
if (abs_n <= max)
n = abs_n;
else
return 0;
}
else
{
n = -n;
if (n >= 0)
/* Carefully avoid signed integer overflow. */
if (min < 0 && abs_n - 1 <= -(min + 1))
n = -1 - (scm_t_intmax)(abs_n - 1);
else
return 0;
}