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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 978B6C65C22 for ; Fri, 2 Nov 2018 17:19:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5EC9F2081F for ; Fri, 2 Nov 2018 17:19:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="fh/2QPYV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5EC9F2081F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org 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 S1728205AbeKCC0z (ORCPT ); Fri, 2 Nov 2018 22:26:55 -0400 Received: from mail-lf1-f68.google.com ([209.85.167.68]:39355 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbeKCC0z (ORCPT ); Fri, 2 Nov 2018 22:26:55 -0400 Received: by mail-lf1-f68.google.com with SMTP id n18so1829186lfh.6 for ; Fri, 02 Nov 2018 10:19:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=7mzEsLKarnAPlT52QMIUPR4InFc78QhESCHV+bCouTg=; b=fh/2QPYVJXnUZqhNPSC3Py8rsv4byEbk/Jt70tUhf7aHeKl/7Hwfbz91wJGOE/Hma4 SYat+RgNMeD0n/eiNpOGDirTDqUb1gLfVVIcpeRPKhnbsVpnTlhl1x0MxGmWkeKvUzKS EnCYAJO5jBeG+MKFzp9ANvl8WKktMbEFphRew= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=7mzEsLKarnAPlT52QMIUPR4InFc78QhESCHV+bCouTg=; b=U4rVIpeRT9HeAenXbwVrtOIrxlhxhsyPPV0CGWxbSoCFPh3z2Qc5F4bpq+lPNg59mw Ms06BSs4ObucRfwdqzSLg+4jfGRzg0VJssBR4d24516v1/S0HGiDlmmrpn6ngMIEDQFM +Fvu94bKBPUVp/G2sJHKDVGyukPxvAV09MX4kvWZf22hnM+9Ir8DPMXrvO1L/gQm8rKd 3gc+A3adc1DiC4CjGBAacvbJ6EmpmHiSNOaRTdb5f3NtnLzA4Br5I9qpvmL5BoSm/kY+ dyv+Sx2uCUSzCrZmFyNxcDAgiWo9JJbuA7yeiNiBEvly/GIPb6MA2TyQ0N44B2O/CCOI s8hg== X-Gm-Message-State: AGRZ1gLM4hjQa7sDpQBxFL/eG+muFBE/k7pjhQeHQ7ewpnyO82DmGnYC EipqFSxFxHUfUDyeyRHNNiN6q7BY1QMfMQ== X-Google-Smtp-Source: AJdET5f93zkdzUblkv2QbzxrBI/y4efjB2PDWi/8bbsVhZ8+ynf391QS5UlGqYSrJYUvqZwU9vzJDg== X-Received: by 2002:a19:ee08:: with SMTP id g8mr7269001lfb.72.1541179140996; Fri, 02 Nov 2018 10:19:00 -0700 (PDT) Received: from mail-lf1-f46.google.com (mail-lf1-f46.google.com. [209.85.167.46]) by smtp.gmail.com with ESMTPSA id g72-v6sm5331986lfl.21.2018.11.02.10.19.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Nov 2018 10:19:00 -0700 (PDT) Received: by mail-lf1-f46.google.com with SMTP id n18so1829138lfh.6 for ; Fri, 02 Nov 2018 10:19:00 -0700 (PDT) X-Received: by 2002:a19:3fcf:: with SMTP id m198mr7130991lfa.106.1541178661753; Fri, 02 Nov 2018 10:11:01 -0700 (PDT) MIME-Version: 1.0 References: <20181101171938-mutt-send-email-mst@kernel.org> <20181102114635.hi3q53kzmz4qljsf@lakrids.cambridge.arm.com> <20181102083018-mutt-send-email-mst@kernel.org> <20181102122937-mutt-send-email-mst@kernel.org> In-Reply-To: <20181102122937-mutt-send-email-mst@kernel.org> From: Linus Torvalds Date: Fri, 2 Nov 2018 10:10:45 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PULL] vhost: cleanups and fixes To: mst@redhat.com Cc: mark.rutland@arm.com, Kees Cook , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, Linux Kernel Mailing List , Andrew Morton , bijan.mottahedeh@oracle.com, gedwards@ddn.com, joe@perches.com, lenaic@lhuard.fr, liang.z.li@intel.com, mhocko@kernel.org, mhocko@suse.com, stefanha@redhat.com, wei.w.wang@intel.com, jasowang@redhat.com 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 Fri, Nov 2, 2018 at 9:59 AM Michael S. Tsirkin wrote: > > Just for completeness I'd like to point out for vhost the copies are > done from the kernel thread. So yes we can switch to copy_to/from_user > but for e.g. 32-bit userspace running on top of a 64 bit kernel it is > IIUC not sufficient - we must *also* do access_ok checks on control path > when addresses are passed to the kernel and when current points to the > correct task struct. Don't you take over the VM with "use_mm()" when you do the copies? So yes, it's a kernel thread, but it has a user VM, and though that should have the user limits. No? Linus