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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 2A552C28CC3 for ; Fri, 31 May 2019 16:46:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0AE8026C68 for ; Fri, 31 May 2019 16:46:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726902AbfEaQqP (ORCPT ); Fri, 31 May 2019 12:46:15 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54506 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbfEaQqP (ORCPT ); Fri, 31 May 2019 12:46:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2DFE0A78; Fri, 31 May 2019 09:46:14 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 48A043F59C; Fri, 31 May 2019 09:46:08 -0700 (PDT) Date: Fri, 31 May 2019 17:46:05 +0100 From: Catalin Marinas To: Andrey Konovalov Cc: Kees Cook , Evgenii Stepanov , Linux ARM , Linux Memory Management List , LKML , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, "open list:KERNEL SELFTEST FRAMEWORK" , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Dmitry Vyukov , Kostya Serebryany , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy , Elliott Hughes , Khalid Aziz Subject: Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Message-ID: <20190531164605.GC3568@arrakis.emea.arm.com> References: <6049844a-65f5-f513-5b58-7141588fef2b@oracle.com> <20190523201105.oifkksus4rzcwqt4@mbp> <20190524101139.36yre4af22bkvatx@mbp> <20190530171540.GD35418@arrakis.emea.arm.com> <20190531161954.GA3568@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Fri, May 31, 2019 at 06:24:06PM +0200, Andrey Konovalov wrote: > On Fri, May 31, 2019 at 6:20 PM Catalin Marinas wrote: > > On Fri, May 31, 2019 at 04:29:10PM +0200, Andrey Konovalov wrote: > > > On Thu, May 30, 2019 at 7:15 PM Catalin Marinas wrote: > > > > On Tue, May 28, 2019 at 04:14:45PM +0200, Andrey Konovalov wrote: > > > > > Thanks for a lot of valuable input! I've read through all the replies > > > > > and got somewhat lost. What are the changes I need to do to this > > > > > series? > > > > > > > > > > 1. Should I move untagging for memory syscalls back to the generic > > > > > code so other arches would make use of it as well, or should I keep > > > > > the arm64 specific memory syscalls wrappers and address the comments > > > > > on that patch? > > > > > > > > Keep them generic again but make sure we get agreement with Khalid on > > > > the actual ABI implications for sparc. > > > > > > OK, will do. I find it hard to understand what the ABI implications > > > are. I'll post the next version without untagging in brk, mmap, > > > munmap, mremap (for new_address), mmap_pgoff, remap_file_pages, shmat > > > and shmdt. > > > > It's more about not relaxing the ABI to accept non-zero top-byte unless > > we have a use-case for it. For mmap() etc., I don't think that's needed > > but if you think otherwise, please raise it. > > > > > > > 2. Should I make untagging opt-in and controlled by a command line argument? > > > > > > > > Opt-in, yes, but per task rather than kernel command line option. > > > > prctl() is a possibility of opting in. > > > > > > OK. Should I store a flag somewhere in task_struct? Should it be > > > inheritable on clone? > > > > A TIF flag would do but I'd say leave it out for now (default opted in) > > until we figure out the best way to do this (can be a patch on top of > > this series). > > You mean leave the whole opt-in/prctl part out? So the only change > would be to move untagging for memory syscalls into generic code? Yes (or just wait until next week to see if the discussion settles down). -- Catalin