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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 F220AC2BA2B for ; Sun, 19 Apr 2020 08:05:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5A7421744 for ; Sun, 19 Apr 2020 08:05:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726012AbgDSIFJ (ORCPT ); Sun, 19 Apr 2020 04:05:09 -0400 Received: from verein.lst.de ([213.95.11.211]:35714 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725903AbgDSIFJ (ORCPT ); Sun, 19 Apr 2020 04:05:09 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 03BEB68BEB; Sun, 19 Apr 2020 10:05:07 +0200 (CEST) Date: Sun, 19 Apr 2020 10:05:06 +0200 From: Christoph Hellwig To: Christophe Leroy Cc: "Eric W. Biederman" , Christoph Hellwig , Arnd Bergmann , x86@kernel.org, linux-kernel@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, Jeremy Kerr Subject: Re: [PATCH 1/2] signal: Factor copy_siginfo_to_external32 from copy_siginfo_to_user32 Message-ID: <20200419080506.GD12222@lst.de> References: <20200414070142.288696-1-hch@lst.de> <20200414070142.288696-3-hch@lst.de> <87pnc5akhk.fsf@x220.int.ebiederm.org> <87k12dakfx.fsf_-_@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 18, 2020 at 10:05:19AM +0200, Christophe Leroy wrote: > > > Le 17/04/2020 à 23:09, Eric W. Biederman a écrit : >> >> To remove the use of set_fs in the coredump code there needs to be a >> way to convert a kernel siginfo to a userspace compat siginfo. >> >> Call that function copy_siginfo_to_compat and factor it out of >> copy_siginfo_to_user32. > > I find it a pitty to do that. > > The existing function could have been easily converted to using > user_access_begin() + user_access_end() and use unsafe_put_user() to copy > to userspace to avoid copying through a temporary structure on the stack. > > With your change, it becomes impossible to do that. As Eric said we need a struct to clear all padding. Note that I though about converting to unsafe_copy_to_user in my variant as we can pretty easily do that if pre-filling the structure earlier. But I didn't want to throw in such unrelated changes for now - I'll volunteer to do it later, though. 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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 42342C2BA2B for ; Sun, 19 Apr 2020 08:16:31 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B5A8B2145D for ; Sun, 19 Apr 2020 08:16:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B5A8B2145D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 494jMw20wDzDqW2 for ; Sun, 19 Apr 2020 18:16:28 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=verein.lst.de; envelope-from=hch@lst.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=lst.de Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 494j6t390kzDrQk for ; Sun, 19 Apr 2020 18:05:10 +1000 (AEST) Received: by verein.lst.de (Postfix, from userid 2407) id 03BEB68BEB; Sun, 19 Apr 2020 10:05:07 +0200 (CEST) Date: Sun, 19 Apr 2020 10:05:06 +0200 From: Christoph Hellwig To: Christophe Leroy Subject: Re: [PATCH 1/2] signal: Factor copy_siginfo_to_external32 from copy_siginfo_to_user32 Message-ID: <20200419080506.GD12222@lst.de> References: <20200414070142.288696-1-hch@lst.de> <20200414070142.288696-3-hch@lst.de> <87pnc5akhk.fsf@x220.int.ebiederm.org> <87k12dakfx.fsf_-_@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Arnd Bergmann , Jeremy Kerr , x86@kernel.org, linux-kernel@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, Christoph Hellwig , "Eric W. Biederman" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sat, Apr 18, 2020 at 10:05:19AM +0200, Christophe Leroy wrote: > > > Le 17/04/2020 à 23:09, Eric W. Biederman a écrit : >> >> To remove the use of set_fs in the coredump code there needs to be a >> way to convert a kernel siginfo to a userspace compat siginfo. >> >> Call that function copy_siginfo_to_compat and factor it out of >> copy_siginfo_to_user32. > > I find it a pitty to do that. > > The existing function could have been easily converted to using > user_access_begin() + user_access_end() and use unsafe_put_user() to copy > to userspace to avoid copying through a temporary structure on the stack. > > With your change, it becomes impossible to do that. As Eric said we need a struct to clear all padding. Note that I though about converting to unsafe_copy_to_user in my variant as we can pretty easily do that if pre-filling the structure earlier. But I didn't want to throw in such unrelated changes for now - I'll volunteer to do it later, though.