From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=x7Zg=6T=vger.kernel.org=linux-fsdevel-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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no
	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 8533CC47254
	for <linux-fsdevel@archiver.kernel.org>; Tue,  5 May 2020 10:48:14 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 6F1F2206B9
	for <linux-fsdevel@archiver.kernel.org>; Tue,  5 May 2020 10:48:14 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1728678AbgEEKsL (ORCPT
        <rfc822;linux-fsdevel@archiver.kernel.org>);
        Tue, 5 May 2020 06:48:11 -0400
Received: from verein.lst.de ([213.95.11.211]:34634 "EHLO verein.lst.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1728238AbgEEKsL (ORCPT <rfc822;linux-fsdevel@vger.kernel.org>);
        Tue, 5 May 2020 06:48:11 -0400
Received: by verein.lst.de (Postfix, from userid 2407)
        id CCFFE68C4E; Tue,  5 May 2020 12:48:05 +0200 (CEST)
Date:   Tue, 5 May 2020 12:48:05 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jann Horn <jannh@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Russell King <linux@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org,
        Mark Salter <msalter@redhat.com>,
        Aurelien Jacquiot <jacquiot.aurelien@gmail.com>,
        linux-c6x-dev@linux-c6x.org,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, linux-sh@vger.kernel.org
Subject: Re: [PATCH v2 1/5] binfmt_elf_fdpic: Stop using dump_emit() on
 user pointers on !MMU
Message-ID: <20200505104805.GA17400@lst.de>
References: <20200429214954.44866-1-jannh@google.com> <20200429214954.44866-2-jannh@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200429214954.44866-2-jannh@google.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-fsdevel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-fsdevel.vger.kernel.org>
X-Mailing-List: linux-fsdevel@vger.kernel.org

On Wed, Apr 29, 2020 at 11:49:50PM +0200, Jann Horn wrote:
> dump_emit() is for kernel pointers, and VMAs describe userspace memory.
> Let's be tidy here and avoid accessing userspace pointers under KERNEL_DS,
> even if it probably doesn't matter much on !MMU systems - especially given
> that it looks like we can just use the same get_dump_page() as on MMU if
> we move it out of the CONFIG_MMU block.

Looks sensible.  Did you get a chance to test this with a nommu setup?