From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?P=E1draig_Brady?= Subject: Re: [PATCH v2] fs: select: fix information leak to userspace Date: Wed, 24 Nov 2010 10:44:50 +0000 Message-ID: <4CECECA2.6070301@draigBrady.com> References: <1289421483-23907-1-git-send-email-segooon@gmail.com> <20101112120834.33062900.akpm@linux-foundation.org> <8D90F8B2-EA29-4EB9-9807-294CE0D5523B@dilger.ca> <20101114092533.GB5323@albatros> <20101114180643.593d19ac.akpm@linux-foundation.org> <1289848341.2607.125.camel@edumazet-laptop> <20101123140111.GA3816@hack> <4CEBD37E.5060107@bfs.de> <203E1F2A-2D04-4B7F-8D1B-9DC24522CB5E@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: wharms@bfs.de, =?ISO-8859-1?Q?Am=E9rico_Wang?= , Eric Dumazet , Andrew Morton , Vasiliy Kulikov , kernel-janitors@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jakub Jelinek To: Andreas Dilger Return-path: Received: from mail1.slb.deg.dub.stisp.net ([84.203.253.98]:7777 "HELO mail1.slb.deg.dub.stisp.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753155Ab0KXKqG (ORCPT ); Wed, 24 Nov 2010 05:46:06 -0500 In-Reply-To: <203E1F2A-2D04-4B7F-8D1B-9DC24522CB5E@dilger.ca> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 23/11/10 18:02, Andreas Dilger wrote: > On 2010-11-23, at 07:45, walter harms wrote: >> Maybe we can convince the gcc people to make 0 padding default. That= will not solve the problems for other compilers but when they claim "w= orks like gcc" we can press then to support this also. I can imagine th= at this will close some other subtle leaks also. >=20 > It makes the most sense to tackle this at the GCC level, since the ad= ded overhead of doing memset(0) on the whole struct may be non-trivial = for commonly-used and/or large structures. Since GCC is already explic= itly zeroing the _used_ fields in the struct, it can much more easily d= etermine whether there is padding in the structure, and zero those few = bytes as needed. Zero padding structs is part of C90. Details here: http://www.pixelbeat.org/programming/gcc/auto_init.html gcc doesn't zero pad when _all_ elements are specified. So perhaps just: - struct timespec rts; - struct timeval rtv; + struct timespec rts =3D {0,}; + struct timeval rtv =3D {0,}; One could also move the rtv declaration to the scope where it's used. cheers, P=E1draig. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html