Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751303AbaGZJTO (ORCPT ); Sat, 26 Jul 2014 05:19:14 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:49836 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750743AbaGZJTM convert rfc822-to-8bit (ORCPT ); Sat, 26 Jul 2014 05:19:12 -0400 X-Originating-IP: 78.210.48.61 Date: Sat, 26 Jul 2014 11:18:45 +0200 From: Guillaume =?iso-8859-1?Q?CL=C9MENT?= To: Malcolm Priestley Cc: Malcolm Priestley , Forest Bond , Greg Kroah-Hartman , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, Dan Carpenter Subject: Re: [PATCH] staging: vt6655: fix direct dereferencing of user pointer Message-ID: <20140726091843.GA5956@pleinair.baobob.org> References: <20140725123301.GZ13737@mwanda> <1406292443-11734-1-git-send-email-gclement@baobob.org> <53D2E3BD.1000208@gmail.com> <20140726082429.GA3121@pleinair.baobob.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20140726082429.GA3121@pleinair.baobob.org> User-Agent: Mutt/1.5.22 (2013-10-16) Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 26, 2014 at 10:24:30AM +0200, Guillaume CL?MENT wrote: > Hi Malcolm, > > On Sat, Jul 26, 2014 at 12:09:49AM +0100, Malcolm Priestley wrote: > > Hi Guillaume > > > > On 25/07/14 13:47, Guillaume Clement wrote: > > > Sparse reported that the data from tagSCmdRequest is given by > > > userspace, so it should be tagged as such. > > extra is not in user space > > > > All right. > > This is still confusing to me because, taking the SIOCSIWGENIE ioctl as > an example, in device_main.c, we have this code: > > rc = iwctl_siwgenie(dev, NULL, &(wrq->u.data), wrq->u.data.pointer); > > Here the extra parameter is the last one, wrq->u.data.pointer. > > I was led to believe that wrq->u.data.pointer is in userspace (this was > reported by sparse actually) because the pointer field in data is > actually defined as __user. > > By the way, the original code (before my patch) reads: if ((wrq->length < 2) || (extra[1]+2 != wrq->length)) { ret = -EINVAL; goto out; } if (wrq->length > MAX_WPA_IE_LEN) { ret = -ENOMEM; goto out; } memset(pMgmt->abyWPAIE, 0, MAX_WPA_IE_LEN); if (copy_from_user(pMgmt->abyWPAIE, extra, wrq->length)) { ret = -EFAULT; goto out; } Note extra[1] and later copy_from_user(x, extra, y). If extra is not in userspace, we should not call copy_from_user, and if it is, we should not dereference it. There is definitely something fishy here. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/