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_PASS,USER_AGENT_MUTT 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 2127BC43381 for ; Fri, 1 Mar 2019 16:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E547820840 for ; Fri, 1 Mar 2019 16:59:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389278AbfCAQ7Q (ORCPT ); Fri, 1 Mar 2019 11:59:16 -0500 Received: from foss.arm.com ([217.140.101.70]:39128 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389170AbfCAQ7Q (ORCPT ); Fri, 1 Mar 2019 11:59:16 -0500 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 D6B7080D; Fri, 1 Mar 2019 08:59:15 -0800 (PST) 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 0CD8F3F575; Fri, 1 Mar 2019 08:59:10 -0800 (PST) Date: Fri, 1 Mar 2019 16:59:08 +0000 From: Catalin Marinas To: Andrey Konovalov Cc: Dave Hansen , Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , Linux ARM , "open list:DOCUMENTATION" , Linux Memory Management List , linux-arch , "open list:KERNEL SELFTEST FRAMEWORK" , LKML , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v10 07/12] fs, arm64: untag user pointers in fs/userfaultfd.c Message-ID: <20190301165908.GA130541@arrakis.emea.arm.com> References: <8343cd77ca301df15839796f3b446b75ce5ffbbf.1550839937.git.andreyknvl@google.com> <73f2f3fe-9a66-22a1-5aae-c282779a75f5@intel.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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 26, 2019 at 03:39:08PM +0100, Andrey Konovalov wrote: > On Sat, Feb 23, 2019 at 12:06 AM Dave Hansen wrote: > > > > On 2/22/19 4:53 AM, Andrey Konovalov wrote: > > > userfaultfd_register() and userfaultfd_unregister() use provided user > > > pointers for vma lookups, which can only by done with untagged pointers. > > > > So, we have to patch all these sites before the tagged values get to the > > point of hitting the vma lookup functions. Dumb question: Why don't we > > just patch the vma lookup functions themselves instead of all of these > > callers? > > That might be a working approach as well. We'll still need to fix up > places where the vma fields are accessed directly. Catalin, what do > you think? Most callers of find_vma*() always follow it by a check of vma->vma_start against some tagged address ('end' in the userfaultfd_(un)register()) case. So it's not sufficient to untag it in find_vma(). -- Catalin