From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753355AbeDSNtJ (ORCPT ); Thu, 19 Apr 2018 09:49:09 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:34573 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753411AbeDSNtH (ORCPT ); Thu, 19 Apr 2018 09:49:07 -0400 Date: Thu, 19 Apr 2018 15:49:02 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Alexander Popov Cc: Wolfram Sang , 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: <20180419134902.6l5jsf4wpqfiaskj@pengutronix.de> References: <1524140962-25639-1-git-send-email-alex.popov@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1524140962-25639-1-git-send-email-alex.popov@linux.com> 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 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 > --- > drivers/i2c/i2c-dev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c > index 036a03f..5790bc8 100644 > --- a/drivers/i2c/i2c-dev.c > +++ b/drivers/i2c/i2c-dev.c > @@ -280,6 +280,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client, > */ > if (msgs[i].flags & I2C_M_RECV_LEN) { > if (!(msgs[i].flags & I2C_M_RD) || > + !msgs[i].len || I'd prefer msgs[i].len > 0 here instead of !msgs[i].len because I can parse that more easily. Semantically the patch is fine and can have my Reviewed-by: Uwe Kleine-König > msgs[i].buf[0] < 1 || > msgs[i].len < msgs[i].buf[0] + > I2C_SMBUS_BLOCK_MAX) { Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |