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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham 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 59EBBC43142 for ; Wed, 27 Jun 2018 15:06:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 12DE825FC4 for ; Wed, 27 Jun 2018 15:06:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="f4rtUxPU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 12DE825FC4 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965588AbeF0PGB (ORCPT ); Wed, 27 Jun 2018 11:06:01 -0400 Received: from mail-io0-f196.google.com ([209.85.223.196]:46987 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965391AbeF0PF6 (ORCPT ); Wed, 27 Jun 2018 11:05:58 -0400 Received: by mail-io0-f196.google.com with SMTP id u23-v6so2197008ioc.13 for ; Wed, 27 Jun 2018 08:05:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=TePJl1h2RCmQRgrewmfbWlz5NvEyMQff5xprdx8Rzxc=; b=f4rtUxPUdJTLqH2GN3ZocuEELaGtPnagDEqgWZzZYD7fGEMTtpV3JCjEkiNXT8Sp1u 11BRrVbkZqFSb9Rt8LJ7AgBUYHSEpUa/RsmzGZd6BqqmA03Li0dkTxjj4TSM/RGhxbF7 guvsQfT3+cYUTrveCPgSfHA+SlZR8LjmWwXbFBFyvdDxa1k1ZS6O/0JdJH/SpBNqj7q6 FbMW4SqazCWUkOVDbSSecPbZ9hhBHRrYqrFOoerynwB8s0yw9di0Gf2XCTTTa/aScRt4 Kidkn+MZvyuJ2W6VNcBTmN7CXe03doy5Je/dy4jB6Fg0w/GFAq2oDVr5L1gQ1ocTXXl0 9F1w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=TePJl1h2RCmQRgrewmfbWlz5NvEyMQff5xprdx8Rzxc=; b=J52LG7HA4Zefz6seNF1qXCw63nmtXOXvxDvdGkeWC6RVyldJcP4zBd3iqrhwwRkqag xvBR+Sham5oJBQva7TKQ8gUxVWooCTLEUk7qx3iO/BumgqXGbw0bMAKAL89r7uhslYH9 GVf5Lls99CMlzkmyGyf7L0ZzdeASfoXsh8dgErTUHl3mac5OhNxwdh461yP4UYJAOM4N nOmOmartVnRHXhc2qnYWZZjp+H2CNRFmSU2cmOnQpvync/0yOzye30kLZbXiQeuEAfSX moqT2o2mKJcW/ehkgueWuBGMmsUIziUUCdEqghoO0u0AY1nics4qpBNxQ95D79phDSpk uzHA== X-Gm-Message-State: APt69E3uvHcCABH7p4uHTz918w9c+bbbKp/2nY/w+/yFFyfaxhI4Yk4F ARplV2Mjfp75To4Tj++AjaHGFUuN5ru7ubAnMeVZoA== X-Google-Smtp-Source: AAOMgpe57m9g/EDqEu7Zvf3nws/5yi6cIZiZ8waZ3JnXOdU/6oKdQOh/DFAcHPxhmBfyFY/ZE52M+ax/NDR6w0et1Sc= X-Received: by 2002:a6b:8495:: with SMTP id o21-v6mr5159519ioi.119.1530111957761; Wed, 27 Jun 2018 08:05:57 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a02:9082:0:0:0:0:0 with HTTP; Wed, 27 Jun 2018 08:05:57 -0700 (PDT) In-Reply-To: <20180626172900.ufclp2pfrhwkxjco@armageddon.cambridge.arm.com> References: <20180626172900.ufclp2pfrhwkxjco@armageddon.cambridge.arm.com> From: Andrey Konovalov Date: Wed, 27 Jun 2018 17:05:57 +0200 Message-ID: Subject: Re: [PATCH v4 0/7] arm64: untag user pointers passed to the kernel To: Catalin Marinas Cc: Will Deacon , Mark Rutland , Robin Murphy , Al Viro , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Linux ARM , linux-doc@vger.kernel.org, Linux Memory Management List , linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, LKML , Chintan Pandya , Jacob Bramley , Ruben Ayrapetyan , Lee Smith , Kostya Serebryany , Dmitry Vyukov , Ramana Radhakrishnan , Evgeniy Stepanov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 26, 2018 at 7:29 PM, Catalin Marinas wrote: > Hi Andrey, > > On Tue, Jun 26, 2018 at 02:47:50PM +0200, Andrey Konovalov wrote: >> On Wed, Jun 20, 2018 at 5:24 PM, Andrey Konovalov wrote: >> > arm64 has a feature called Top Byte Ignore, which allows to embed pointer >> > tags into the top byte of each pointer. Userspace programs (such as >> > HWASan, a memory debugging tool [1]) might use this feature and pass >> > tagged user pointers to the kernel through syscalls or other interfaces. >> > >> > This patch makes a few of the kernel interfaces accept tagged user >> > pointers. The kernel is already able to handle user faults with tagged >> > pointers and has the untagged_addr macro, which this patchset reuses. >> > >> > We're not trying to cover all possible ways the kernel accepts user >> > pointers in one patchset, so this one should be considered as a start. >> > >> > Thanks! >> > >> > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html >> >> Is there anything I should do to move forward with this? >> >> I've received zero replies to this patch set (v3 and v4) over the last >> month. > > The patches in this series look fine but my concern is that they are not > sufficient and we don't have (yet?) a way to identify where such > annotations are required. You even say in patch 6 that this is "some > initial work for supporting non-zero address tags passed to the kernel". > Unfortunately, merging (or relaxing) an ABI without a clear picture is > not really feasible. > > While I support this work, as a maintainer I'd like to understand > whether we'd be in a continuous chase of ABI breaks with every kernel > release or we have a better way to identify potential issues. Is there > any way to statically analyse conversions from __user ptr to long for > example? Or, could we get the compiler to do this for us? OK, got it, I'll try to figure out a way to find these conversions. Thanks!