From: Eric Blake <eblake@redhat.com>
To: Hannes Reinecke <hare@suse.de>, Andreas Faerber <afaerber@suse.de>
Cc: qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>
Subject: Re: [Qemu-devel] [PATCH] qdev: Validate hex properties
Date: Tue, 26 Nov 2013 08:15:27 -0700 [thread overview]
Message-ID: <5294BB0F.1000805@redhat.com> (raw)
In-Reply-To: <1385478338-27433-1-git-send-email-hare@suse.de>
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On 11/26/2013 08:05 AM, Hannes Reinecke wrote:
> strtoull() might return '-1' to signify an overflow.
Yes, but -1 (aka ULLONG_MAX) is also a valid return when there is not
overflow, so testing for -1 is NOT a reliable indicator on whether
overflow occurred. Also, you mention strtoull() here...
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
> hw/core/qdev-properties.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index dc8ae69..5761295 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -202,6 +202,9 @@ static int parse_hex8(DeviceState *dev, Property *prop, const char *str)
> if ((*end != '\0') || (end == str)) {
...but this was calling strtoul().
> return -EINVAL;
> }
> + if (*ptr == (uint8_t)-1) {
> + return -ERANGE;
> + }
NAK. This is NOT how you check for overflow with strtoull. Instead,
you should use:
errno = 0;
*ptr = strtoul(str, &end, 16);
if (errno) {
return -errno;
}
if (!*end || end == str) {
return -EINVAL;
}
return 0;
>
> return 0;
> }
> @@ -333,6 +336,9 @@ static int parse_hex32(DeviceState *dev, Property *prop, const char *str)
> if ((*end != '\0') || (end == str)) {
> return -EINVAL;
> }
> + if (*ptr == (uint32_t)-1) {
> + return -ERANGE;
> + }
NAK. And this function is even MORE broken. On a 32-bit platform,
assigning the results of strtol() into a uint32_t may result in silent
truncation. If you are trying to detect overflow, you MUST assign the
results into a long, then check that the long does not overflow
uint32_t, rather than checking (too late) whether the uint32_t has
already been overflowed.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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prev parent reply other threads:[~2013-11-26 15:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-26 15:05 [Qemu-devel] [PATCH] qdev: Validate hex properties Hannes Reinecke
2013-11-26 15:15 ` Peter Maydell
2013-11-26 15:15 ` Eric Blake [this message]
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