From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
"Ardelean, Alexandru" <alexandru.Ardelean@analog.com>,
"lars@metafoo.de" <lars@metafoo.de>,
"kernel-janitors@vger.kernel.org"
<kernel-janitors@vger.kernel.org>,
"Popa, Stefan Serban" <StefanSerban.Popa@analog.com>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
"pmeerw@pmeerw.net" <pmeerw@pmeerw.net>,
"knaack.h@gmx.de" <knaack.h@gmx.de>
Subject: Re: [PATCH] iio: imu: adis16480: clean up a condition
Date: Mon, 7 Oct 2019 17:18:03 +0300 [thread overview]
Message-ID: <20191007141803.GZ22609@kadam> (raw)
In-Reply-To: <20191007102107.000067b6@huawei.com>
On Mon, Oct 07, 2019 at 10:21:07AM +0100, Jonathan Cameron wrote:
> On Sun, 6 Oct 2019 21:14:40 +0300
> Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> > On Sun, Oct 06, 2019 at 09:51:33AM +0100, Jonathan Cameron wrote:
> > > On Thu, 26 Sep 2019 14:36:30 +0300
> > > Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > >
> > > > On Thu, Sep 26, 2019 at 11:06:39AM +0000, Ardelean, Alexandru wrote:
> > > > > On Thu, 2019-09-26 at 11:10 +0300, Dan Carpenter wrote:
> > > > > > [External]
> > > > > >
> > > > > > The "t" variable is unsigned so it can't be less than zero. We really
> > > > > > are just trying to prevent divide by zero bugs so just checking against
> > > > > > zero is sufficient.
> > >
> > > I'm not sure that true. It if were signed we'd be detecting that the
> > > input from userspace was negative.
> >
> > It does a really bad job of that though so it raises more questions than
> > answers. Maybe just one of the parameters is negative or maybe the
> > multiply or the addition overflowed? Should scenarios those be checked?
> >
> > It turns out none of those situations matter, only divide by zero needs
> > to be checked.
>
> It isn't being nearly paranoid enough. Either val or val2 being
> negative is a reason to fault out. Divide by zero needs handling after
> that. Obviously divide by zero is the only one that causes a crash but
> negatives are going to cause rather 'unexpected' results.
The result is that it gets capped at st->chip_info->max_dec_rate so it's
not a horrible result. :P I don't know if it's unexpected or not.
regards,
dan carpenter
WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
"Ardelean, Alexandru" <alexandru.Ardelean@analog.com>,
"lars@metafoo.de" <lars@metafoo.de>,
"kernel-janitors@vger.kernel.org"
<kernel-janitors@vger.kernel.org>,
"Popa, Stefan Serban" <StefanSerban.Popa@analog.com>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
"pmeerw@pmeerw.net" <pmeerw@pmeerw.net>,
"knaack.h@gmx.de" <knaack.h@gmx.de>
Subject: Re: [PATCH] iio: imu: adis16480: clean up a condition
Date: Mon, 07 Oct 2019 14:18:03 +0000 [thread overview]
Message-ID: <20191007141803.GZ22609@kadam> (raw)
In-Reply-To: <20191007102107.000067b6@huawei.com>
On Mon, Oct 07, 2019 at 10:21:07AM +0100, Jonathan Cameron wrote:
> On Sun, 6 Oct 2019 21:14:40 +0300
> Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> > On Sun, Oct 06, 2019 at 09:51:33AM +0100, Jonathan Cameron wrote:
> > > On Thu, 26 Sep 2019 14:36:30 +0300
> > > Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > >
> > > > On Thu, Sep 26, 2019 at 11:06:39AM +0000, Ardelean, Alexandru wrote:
> > > > > On Thu, 2019-09-26 at 11:10 +0300, Dan Carpenter wrote:
> > > > > > [External]
> > > > > >
> > > > > > The "t" variable is unsigned so it can't be less than zero. We really
> > > > > > are just trying to prevent divide by zero bugs so just checking against
> > > > > > zero is sufficient.
> > >
> > > I'm not sure that true. It if were signed we'd be detecting that the
> > > input from userspace was negative.
> >
> > It does a really bad job of that though so it raises more questions than
> > answers. Maybe just one of the parameters is negative or maybe the
> > multiply or the addition overflowed? Should scenarios those be checked?
> >
> > It turns out none of those situations matter, only divide by zero needs
> > to be checked.
>
> It isn't being nearly paranoid enough. Either val or val2 being
> negative is a reason to fault out. Divide by zero needs handling after
> that. Obviously divide by zero is the only one that causes a crash but
> negatives are going to cause rather 'unexpected' results.
The result is that it gets capped at st->chip_info->max_dec_rate so it's
not a horrible result. :P I don't know if it's unexpected or not.
regards,
dan carpenter
next prev parent reply other threads:[~2019-10-07 14:18 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-26 8:10 [PATCH] iio: imu: adis16480: clean up a condition Dan Carpenter
2019-09-26 8:10 ` Dan Carpenter
2019-09-26 11:06 ` Ardelean, Alexandru
2019-09-26 11:06 ` Ardelean, Alexandru
2019-09-26 11:36 ` Dan Carpenter
2019-09-26 11:36 ` Dan Carpenter
2019-10-06 8:51 ` Jonathan Cameron
2019-10-06 8:51 ` Jonathan Cameron
2019-10-06 18:14 ` Dan Carpenter
2019-10-06 18:14 ` Dan Carpenter
2019-10-07 9:21 ` Jonathan Cameron
2019-10-07 9:21 ` Jonathan Cameron
2019-10-07 14:18 ` Dan Carpenter [this message]
2019-10-07 14:18 ` Dan Carpenter
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