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Mon, 7 Oct 2019 14:18:20 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 2vf4phm9sy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 07 Oct 2019 14:18:20 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x97EICHO005519; Mon, 7 Oct 2019 14:18:12 GMT Received: from kadam (/41.57.98.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 07 Oct 2019 07:18:11 -0700 Date: Mon, 7 Oct 2019 17:18:03 +0300 From: Dan Carpenter To: Jonathan Cameron Cc: Jonathan Cameron , "Ardelean, Alexandru" , "lars@metafoo.de" , "kernel-janitors@vger.kernel.org" , "Popa, Stefan Serban" , "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Hennerich, Michael" , "pmeerw@pmeerw.net" , "knaack.h@gmx.de" Subject: Re: [PATCH] iio: imu: adis16480: clean up a condition Message-ID: <20191007141803.GZ22609@kadam> References: <20190926081016.GA2332@mwanda> <9e40c550310d6f30e6481329e01061beb474bc33.camel@analog.com> <20190926113630.GF27389@kadam> <20191006095133.24fb89be@archlinux> <20191006181439.GU22609@kadam> <20191007102107.000067b6@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191007102107.000067b6@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9402 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=930 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910070142 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9402 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910070142 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 07, 2019 at 10:21:07AM +0100, Jonathan Cameron wrote: > On Sun, 6 Oct 2019 21:14:40 +0300 > Dan Carpenter 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 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