From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=sxVn=TW=vger.kernel.org=linux-kernel-owner@kernel.org>
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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,
	USER_AGENT_NEOMUTT 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 F368CC46460
	for <linux-kernel@archiver.kernel.org>; Wed, 22 May 2019 12:09:18 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id C5418217D4
	for <linux-kernel@archiver.kernel.org>; Wed, 22 May 2019 12:09:18 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1729301AbfEVMJS (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Wed, 22 May 2019 08:09:18 -0400
Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:49132 "EHLO
        foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727464AbfEVMJR (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 22 May 2019 08:09:17 -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 74CBF80D;
        Wed, 22 May 2019 05:09:16 -0700 (PDT)
Received: from mbp (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70])
        by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AA7D73F575;
        Wed, 22 May 2019 05:09:10 -0700 (PDT)
Date:   Wed, 22 May 2019 13:09:07 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     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 <vincenzo.frascino@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kees Cook <keescook@chromium.org>,
        Yishai Hadas <yishaih@mellanox.com>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        Alexander Deucher <Alexander.Deucher@amd.com>,
        Christian Koenig <Christian.Koenig@amd.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Leon Romanovsky <leon@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Kostya Serebryany <kcc@google.com>,
        Evgeniy Stepanov <eugenis@google.com>,
        Lee Smith <Lee.Smith@arm.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
        Jacob Bramley <Jacob.Bramley@arm.com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Subject: Re: [PATCH v15 09/17] fs, arm64: untag user pointers in
 copy_mount_options
Message-ID: <20190522120907.tf3tb3h5oxhfokgw@mbp>
References: <cover.1557160186.git.andreyknvl@google.com>
 <ac2ca3454b1ae8856ea2e29a1316fea50a30c788.1557160186.git.andreyknvl@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <ac2ca3454b1ae8856ea2e29a1316fea50a30c788.1557160186.git.andreyknvl@google.com>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, May 06, 2019 at 06:30:55PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
> 
> In copy_mount_options a user address is being subtracted from TASK_SIZE.
> If the address is lower than TASK_SIZE, the size is calculated to not
> allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
> However if the address is tagged, then the size will be calculated
> incorrectly.
> 
> Untag the address before subtracting.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>