From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752142AbeD3HNQ (ORCPT ); Mon, 30 Apr 2018 03:13:16 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:60569 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751698AbeD3HNP (ORCPT ); Mon, 30 Apr 2018 03:13:15 -0400 Date: Mon, 30 Apr 2018 09:13:10 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Wolfram Sang Cc: Alexander Popov , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, sil2review@lists.osadl.org, Dmitry Vyukov , syzkaller@googlegroups.com Subject: Re: [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr() Message-ID: <20180430071310.7s7glgig3cilw4dj@pengutronix.de> References: <1524140962-25639-1-git-send-email-alex.popov@linux.com> <20180427120658.wi32f7margtfazzp@ninjato> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180427120658.wi32f7margtfazzp@ninjato> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 27, 2018 at 02:06:58PM +0200, Wolfram Sang wrote: > On Thu, Apr 19, 2018 at 03:29:22PM +0300, Alexander Popov wrote: > > i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which > > returns ZERO_SIZE_PTR if i2c_msg.len is zero. > > > > Currently i2cdev_ioctl_rdwr() always dereferences the buf pointer in case > > of I2C_M_RD | I2C_M_RECV_LEN transfer. That causes a kernel oops in > > case of zero len. > > > > Let's check the len against zero before dereferencing buf pointer. > > > > This issue was triggered by syzkaller. > > > > Signed-off-by: Alexander Popov > > Applied to for-current with the arithmetic expression changed to '< 1' > to keep in sync with the previous one. Will push out soon, so you can > double check if you are interested. Thanks, I like it. An added bonus is also that you don't need to think about the type of msgs[i].len and what happens if it is negative. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |