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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 D6B87C04E87 for ; Tue, 21 May 2019 18:49:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF2E7217F5 for ; Tue, 21 May 2019 18:49:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="JYscqSP1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728055AbfEUStA (ORCPT ); Tue, 21 May 2019 14:49:00 -0400 Received: from mail-qk1-f196.google.com ([209.85.222.196]:38828 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728283AbfEUSs7 (ORCPT ); Tue, 21 May 2019 14:48:59 -0400 Received: by mail-qk1-f196.google.com with SMTP id a64so11737321qkg.5 for ; Tue, 21 May 2019 11:48:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Brh6Wum1Zthj/uQ2mtyHFIq9uQlvrAXKSZbEsVapKL8=; b=JYscqSP1HPPRVqGuMd5owD3l/IDlGmL6FFL67m798Jm2AP4qGcOTqtawfRNo+5kAFu iEJ0vUz9qOZ+rvajt/fb76zKILX2m7sPHzCjQLxU/xpu8s+X3lkRy9CgqtNpDaf0XFJu m/SIilww4DfdKs62gi8wE4MGevsPrJgDS2TyvhL/7eUtavobHZ7DqCVwKBcDulDJUjVu MVt0CUr2fUDTtnd4Vvag66g4rnBT/cZ1xH3t4yZwYbfafoegD76V6HRafoLD0R1dZ62Z EbRvObIPEul9wb7eEhcBGsIGomq6YRkOd3NfdawsXW6Hn11cNpJ1sY5CjCpDM4tjfGZL aezw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=Brh6Wum1Zthj/uQ2mtyHFIq9uQlvrAXKSZbEsVapKL8=; b=IfBTF/pJ9H/GH1zTbcnA0pA1mn8NiAmBCM632N/C3W/H9U/clGEvcMYyP1UpQd9rBX EXqKRpzyqBbpXCGGDS/SMUhrDjvJL8WSeuINChUx4CnmQuWnBEC2pc1T6Aa4FcDj3jis Q8pISolWpc18/9WSMmQbgNKflmwHJVDDWBy8Rx+31lVpYuRePjGxrcfEk2QUchCzp8zT TJBdc/QGLd7zU0c8mJLwZtfRHfnGZmiDYvRuRclW4r/NKIdt+bPdCzQgyLntzCnupZ3N eBFjxuCB8vyHBaS8P8fyFxZrtXMEF5m6/e+/j1K7Jbavp+jRktM4OlTB0efOcrVh68if 7d7A== X-Gm-Message-State: APjAAAX+VCKI5/JPInGyY04GkO9VdN7JEkBbOw9o7Y+k4Webrf3y/KOn a77TSLvBUUsipK3JPZUHR7doKw== X-Google-Smtp-Source: APXvYqwU77tWKnZY68/uvl8nI3fxF+k0K8AI67X6RVtQAbCKMK/pPRLs+1/gDbqNIuNCiuScF9EnOQ== X-Received: by 2002:a37:358:: with SMTP id 85mr63206066qkd.174.1558464538599; Tue, 21 May 2019 11:48:58 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-156-34-49-251.dhcp-dynamic.fibreop.ns.bellaliant.net. [156.34.49.251]) by smtp.gmail.com with ESMTPSA id u2sm5545370qtq.45.2019.05.21.11.48.57 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 21 May 2019 11:48:57 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hT9om-0004QR-Qs; Tue, 21 May 2019 15:48:56 -0300 Date: Tue, 21 May 2019 15:48:56 -0300 From: Jason Gunthorpe To: Catalin Marinas Cc: Andrey Konovalov , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Message-ID: <20190521184856.GC2922@ziepe.ca> References: <20190517144931.GA56186@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190517144931.GA56186@arrakis.emea.arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Fri, May 17, 2019 at 03:49:31PM +0100, Catalin Marinas wrote: > The tagged pointers (whether hwasan or MTE) should ideally be a > transparent feature for the application writer but I don't think we can > solve it entirely and make it seamless for the multitude of ioctls(). > I'd say you only opt in to such feature if you know what you are doing > and the user code takes care of specific cases like ioctl(), hence the > prctl() proposal even for the hwasan. I'm not sure such a dire view is warrented.. The ioctl situation is not so bad, other than a few special cases, most drivers just take a 'void __user *' and pass it as an argument to some function that accepts a 'void __user *'. sparse et al verify this. As long as the core functions do the right thing the drivers will be OK. The only place things get dicy is if someone casts to unsigned long (ie for vma work) but I think that reflects that our driver facing APIs for VMAs are compatible with static analysis (ie I have no earthly idea why get_user_pages() accepts an unsigned long), not that this is too hard. Jason