From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751164Ab3KMUYm (ORCPT ); Wed, 13 Nov 2013 15:24:42 -0500 Received: from mail-pb0-f45.google.com ([209.85.160.45]:52582 "EHLO mail-pb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881Ab3KMUYg (ORCPT ); Wed, 13 Nov 2013 15:24:36 -0500 Date: Wed, 13 Nov 2013 12:24:35 -0800 From: Guenter Roeck To: Kees Cook Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] gcc4: Disable __compiletime_object_size for GCC 4.6+ Message-ID: <20131113202435.GB5322@roeck-us.net> References: <1365821348-7177-1-git-send-email-linux@roeck-us.net> <20131113183913.GK4994@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131113183913.GK4994@outflux.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 13, 2013 at 10:39:13AM -0800, Kees Cook wrote: > Hi Guenter, > > On Fri, Apr 12, 2013 at 07:49:08PM -0700, Guenter Roeck wrote: > > __builtin_object_size is known to be broken on gcc 4.6+. > > See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48880 for details. > > > > This causes unnecssary build warnings and errors such as > > > > In function 'copy_from_user', inlined from 'sb16_copy_from_user' > > at sound/oss/sb_audio.c:878:22: > > arch/x86/include/asm/uaccess_32.h:211:26: error: call to 'copy_from_user_overflow' > > declared with attribute error: copy_from_user() buffer size is not provably correct > > make[3]: [sound/oss/sb_audio.o] Error 1 (ignored) > > > > Disable it where broken. > > Is there an alternative? This means that things like > DEBUG_STRICT_USER_COPY_CHECKS are being rendered useless. I don't think > this is _always_ broken, just under certain situations, right? > There was a recent proposal to address the problem differently and then revert this patch. Not sure what happened with it. I can try digging it up if necessary. Guenter