From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751468AbeBXIyM (ORCPT ); Sat, 24 Feb 2018 03:54:12 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:55558 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772AbeBXIyK (ORCPT ); Sat, 24 Feb 2018 03:54:10 -0500 Date: Sat, 24 Feb 2018 11:45:16 +0300 From: Dan Carpenter To: "Luis R. Rodriguez" Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, cocci@systeme.lip6.fr Subject: Re: [PATCH] lib/test_kmod: Fix an integer overflow test Message-ID: <20180224084516.pex3ogxzipzj2o5y@mwanda> References: <20180122102754.GD23912@mwanda> <20180224025941.GB14069@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180224025941.GB14069@wotan.suse.de> User-Agent: NeoMutt/20170609 (1.8.3) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8813 signatures=668678 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=795 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1802240114 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 24, 2018 at 02:59:41AM +0000, Luis R. Rodriguez wrote: > On Mon, Jan 22, 2018 at 01:27:54PM +0300, Dan Carpenter wrote: > > The main problem is that the parentheses are in the wrong place and the > > unlikely() call returns either 0 or 1 so it's never less than zero. > > Doh, thanks, yes. Seems worth considering a grammar rule for it. > > > The other problem is that signed integer overflows like "INT_MAX + 1" are > > undefined behavior. > > Likewise. > > This seems like another possible generic typo issue. But I would not resolve it > the way you did, in this particular case below num_test_devs represents the > number of already registered devs, before we increment. So the way to resolve > this would be: > > if (num_test_devs + 1 == INT_MAX) > > I'll get this upstream, thanks! There is no issue if num_test_devs is INT_MAX. But capping it at INT_MAX - 1 is also fine. regards, dan carpenter