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=-7.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 CAA26C433EF for ; Fri, 10 Sep 2021 10:27:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A66F5610E9 for ; Fri, 10 Sep 2021 10:27:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232291AbhIJK2U (ORCPT ); Fri, 10 Sep 2021 06:28:20 -0400 Received: from pegase2.c-s.fr ([93.17.235.10]:38177 "EHLO pegase2.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232157AbhIJK2R (ORCPT ); Fri, 10 Sep 2021 06:28:17 -0400 Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4H5X9j2q1rz9sVM; Fri, 10 Sep 2021 12:27:05 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 88gl3r46r1PN; Fri, 10 Sep 2021 12:27:05 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4H5X9j1NDRz9sV6; Fri, 10 Sep 2021 12:27:05 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 140988B781; Fri, 10 Sep 2021 12:27:05 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ECM4fsn4G9tT; Fri, 10 Sep 2021 12:27:05 +0200 (CEST) Received: from localhost.localdomain (po22017.idsi0.si.c-s.fr [192.168.7.20]) by messagerie.si.c-s.fr (Postfix) with ESMTP id AACA18B763; Fri, 10 Sep 2021 12:27:04 +0200 (CEST) Subject: Re: [PATCH v2 3/5] signal: Add unsafe_copy_siginfo_to_user() To: "Eric W. Biederman" Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <87mtoux1hi.fsf@disp2133> <2715792c-eb10-eeb8-3d49-24486abe953b@csgroup.eu> <877dfrrkxo.fsf@disp2133> From: Christophe Leroy Message-ID: <7caf5127-36fc-7c77-00f1-7be82d6f26e0@csgroup.eu> Date: Fri, 10 Sep 2021 10:27:03 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <877dfrrkxo.fsf@disp2133> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/8/21 6:17 PM, Eric W. Biederman wrote: > Christophe Leroy writes: > >> Le 02/09/2021 à 20:43, Eric W. Biederman a écrit : >>> Christophe Leroy writes: >>> >>>> In the same spirit as commit fb05121fd6a2 ("signal: Add >>>> unsafe_get_compat_sigset()"), implement an 'unsafe' version of >>>> copy_siginfo_to_user() in order to use it within user access blocks. >>>> >>>> For that, also add an 'unsafe' version of clear_user(). >>> >>> Looking at your use cases you need the 32bit compat version of this >>> as well. >>> >>> The 32bit compat version is too complicated to become a macro, so I >>> don't think you can make this work correctly for the 32bit compat case. >> >> When looking into patch 5/5 that you nacked, I think you missed the fact that we >> keep using copy_siginfo_to_user32() as it for the 32 bit compat case. > > I did. My mistake. > > However that mistake was so easy I think it mirrors the comments others > have made that this looks like a maintenance hazard. > > Is improving the performance of 32bit kernels interesting? Yes it is, and that's what this series do. > Is improving the performance of 32bit compat support interesting? For me this is a corner case, so I left it aside for now. > > If performance one or either of those cases is interesting it looks like > we already have copy_siginfo_to_external32 the factor you would need > to build unsafe_copy_siginfo_to_user32. I'm not sure I understand your saying here. What do you expect me to do with copy_siginfo_to_external32() ? copy_siginfo_to_user32() is for compat only. Native 32 bits powerpc use copy_siginfo_to_user() > > So I am not going to say impossible but please make something > maintainable. I unified all of the compat 32bit siginfo logic because > it simply did not get enough love and attention when it was implemented > per architecture. Yes, and ? I didn't do any modification to the compat case, so what you did remains. > > In general I think that concern applies to this case as well. We really > need an implementation that shares as much burden as possible with other > architectures. I think yes, that's the reason why I made a generic unsafe_copy_siginfo_to_user() and didn't make a powerpc dedicated change. Once this is merged any other architecture can use unsafe_copy_siginfo_to_user(). Did I miss something ? Christophe