From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755176Ab0IOWmV (ORCPT ); Wed, 15 Sep 2010 18:42:21 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:39228 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1754939Ab0IOWmR (ORCPT ); Wed, 15 Sep 2010 18:42:17 -0400 X-Authenticated: #10250065 X-Provags-ID: V01U2FsdGVkX18SVXkB3SISfb+cRxv7DQBkEZxvxypjGnu2vFOURi VCDJVv/QF2jKtV Message-ID: <4C914BC4.8070809@gmx.de> Date: Thu, 16 Sep 2010 00:42:12 +0200 From: Florian Tobias Schandinat User-Agent: Mozilla-Thunderbird 2.0.0.24 (X11/20100328) MIME-Version: 1.0 To: Dan Rosenberg CC: JosephChan@via.com.tw, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, security@kernel.org, stable@kernel.org Subject: Re: [PATCH] drivers/video/via/ioctl.c: prevent reading uninitialized stack memory References: <1284587059.6275.101.camel@dan> In-Reply-To: <1284587059.6275.101.camel@dan> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Dan Rosenberg schrieb: > The VIAFB_GET_INFO device ioctl allows unprivileged users to read 1968 > bytes of uninitialized stack memory, because the "reserved" member of > the viafb_ioctl_info struct declared on the stack is not altered or > zeroed before being copied back to the user. This patch takes care of > it. I am wondering about the number of bytes as sizeof(struct viafb_ioctl_info) = 256 so it should be a bit less. But that's just nitpicking, the issue is certainly real. Your patch does the right thing but there is a bug in it: > Signed-off-by: Dan Rosenberg > > --- linux-2.6.35.4.orig/drivers/video/via/ioctl.c 2010-08-26 19:47:12.000000000 -0400 > +++ linux-2.6.35.4/drivers/video/via/ioctl.c 2010-09-15 11:53:29.997375748 -0400 > @@ -25,6 +25,8 @@ int viafb_ioctl_get_viafb_info(u_long ar > { > struct viafb_ioctl_info viainfo; > > + memset(&viainfo, 0, sizeof(struct viafb_ioctl)); Shouldn't it be sizeof(struct viafb_ioctl_info) or sizeof(viainfo) ? At least here it does not even compile otherwise.... Thanks, Florian Tobias Schandinat