From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FD36C282C0 for ; Wed, 23 Jan 2019 15:44:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCEC321855 for ; Wed, 23 Jan 2019 15:44:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726802AbfAWPoq convert rfc822-to-8bit (ORCPT ); Wed, 23 Jan 2019 10:44:46 -0500 Received: from mga06.intel.com ([134.134.136.31]:53707 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726790AbfAWPoq (ORCPT ); Wed, 23 Jan 2019 10:44:46 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jan 2019 07:44:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,511,1539673200"; d="scan'208";a="140646916" Received: from jnikula-mobl3.fi.intel.com (HELO localhost) ([10.237.66.172]) by fmsmga001.fm.intel.com with ESMTP; 23 Jan 2019 07:44:31 -0800 From: Jani Nikula To: Edwin Zimmerman , 'Greg KH' , 'Kees Cook' Cc: dev@openvswitch.org, 'Ard Biesheuvel' , netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, intel-wired-lan@lists.osuosl.org, linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org, 'Laura Abbott' , linux-kbuild@vger.kernel.org, 'Alexander Popov' Subject: RE: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches In-Reply-To: <000001d4b32a$845e06e0$8d1a14a0$@211mainstreet.net> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20190123110349.35882-1-keescook@chromium.org> <20190123110349.35882-2-keescook@chromium.org> <20190123115829.GA31385@kroah.com> <874l9z31c5.fsf@intel.com> <000001d4b32a$845e06e0$8d1a14a0$@211mainstreet.net> Date: Wed, 23 Jan 2019 17:46:14 +0200 Message-ID: <87va2f1int.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Wed, 23 Jan 2019, Edwin Zimmerman wrote: > On Wed, 23 Jan 2019, Jani Nikula wrote: >> On Wed, 23 Jan 2019, Greg KH wrote: >> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote: >> >> Variables declared in a switch statement before any case statements >> >> cannot be initialized, so move all instances out of the switches. >> >> After this, future always-initialized stack variables will work >> >> and not throw warnings like this: >> >> >> >> fs/fcntl.c: In function ‘send_sigio_to_task’: >> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable] >> >> siginfo_t si; >> >> ^~ >> > >> > That's a pain, so this means we can't have any new variables in { } >> > scope except for at the top of a function? >> > >> > That's going to be a hard thing to keep from happening over time, as >> > this is valid C :( >> >> Not all valid C is meant to be used! ;) > > Very true. The other thing to keep in mind is the burden of enforcing > a prohibition on a valid C construct like this. It seems to me that > patch reviewers and maintainers have enough to do without forcing them > to watch for variable declarations in switch statements. Automating > this prohibition, should it be accepted, seems like a good idea to me. Considering that the treewide diffstat to fix this is: 18 files changed, 45 insertions(+), 46 deletions(-) and using the gcc plugin in question will trigger the switch-unreachable warning, I think we're good. There'll probably be the occasional declarations that pass through, and will get fixed afterwards. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center