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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 D3DA2ECDE20 for ; Wed, 11 Sep 2019 13:03:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B57D8206A1 for ; Wed, 11 Sep 2019 13:03:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728044AbfIKNDT (ORCPT ); Wed, 11 Sep 2019 09:03:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41160 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726954AbfIKNDS (ORCPT ); Wed, 11 Sep 2019 09:03:18 -0400 Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7E374C065128 for ; Wed, 11 Sep 2019 13:03:17 +0000 (UTC) Received: by mail-qk1-f198.google.com with SMTP id n125so24880519qkc.16 for ; Wed, 11 Sep 2019 06:03:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/sfNjqGMZWLcI3m0N4VrOWVEum1o031nknNQPF2WES8=; b=GQC/Wz/VpFLbJ8c3EQZ5alB2VDrsoe28F/uReifmt/Fr23Yl4uSwhHT1XtFqiWqA0n jnZRZSLuXXMOfu6b6I/vhQKW6zrBUbmDXQoqXv78ZJjzYlqW7xc7SEL+8dp+kOrRyMrq 12XObBD5C+arX7THJiLmvVe+c6L8otjE5zrvQmgsfzwaTRnOsevfUv3Je0ItqopSpbV2 kUkbafDkwkyEatxw2cNBuzwi//3yBw1z1TgUx5/Kzky3NORXFdhs7LxaG7CdbqyiXYdg cak/yCWX7jZ+Cs9/3WbvXRNjKEBrQjb1V3Hw2dEEBGcQnfLgZ82iGTHkNUTZVXQkVfon Mm4g== X-Gm-Message-State: APjAAAVt0lIP9ZTFdYmZqFnfQkiMN+K+Jh15HZNCPejtvvt0Azp+P4zM RPhUtk5VdJbVhFYIozd+qtBwahfLRe3L4p84glL6Rq/B2tfwhQxSpkS+oHa4nlAmw8KCyApaHKM jDBjwDHcdNpVoAHvcY1Eebpsy X-Received: by 2002:ac8:7242:: with SMTP id l2mr35745592qtp.4.1568206996777; Wed, 11 Sep 2019 06:03:16 -0700 (PDT) X-Google-Smtp-Source: APXvYqwmsmhjoHJTb7z6oORqOFoKPWxTBsyQouHREJ+8K5GPemL48MacSn+bJagBRzKL996ErgPJyA== X-Received: by 2002:ac8:7242:: with SMTP id l2mr35745571qtp.4.1568206996537; Wed, 11 Sep 2019 06:03:16 -0700 (PDT) Received: from redhat.com ([80.74.107.118]) by smtp.gmail.com with ESMTPSA id v2sm6615278qtv.22.2019.09.11.06.03.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Sep 2019 06:03:15 -0700 (PDT) Date: Wed, 11 Sep 2019 09:03:10 -0400 From: "Michael S. Tsirkin" To: Michal Hocko Cc: linux-kernel@vger.kernel.org, Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH v2] vhost: block speculation of translated descriptors Message-ID: <20190911085807-mutt-send-email-mst@kernel.org> References: <20190911120908.28410-1-mst@redhat.com> <20190911121628.GT4023@dhcp22.suse.cz> <20190911082236-mutt-send-email-mst@kernel.org> <20190911123316.GX4023@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190911123316.GX4023@dhcp22.suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 11, 2019 at 02:33:16PM +0200, Michal Hocko wrote: > On Wed 11-09-19 08:25:03, Michael S. Tsirkin wrote: > > On Wed, Sep 11, 2019 at 02:16:28PM +0200, Michal Hocko wrote: > > > On Wed 11-09-19 08:10:00, Michael S. Tsirkin wrote: > > > > iovec addresses coming from vhost are assumed to be > > > > pre-validated, but in fact can be speculated to a value > > > > out of range. > > > > > > > > Userspace address are later validated with array_index_nospec so we can > > > > be sure kernel info does not leak through these addresses, but vhost > > > > must also not leak userspace info outside the allowed memory table to > > > > guests. > > > > > > > > Following the defence in depth principle, make sure > > > > the address is not validated out of node range. > > > > > > > > Signed-off-by: Michael S. Tsirkin > > > > Acked-by: Jason Wang > > > > Tested-by: Jason Wang > > > > > > no need to mark fo stable? Other spectre fixes tend to be backported > > > even when the security implications are not really clear. The risk > > > should be low and better to be covered in case. > > > > This is not really a fix - more a defence in depth thing, > > quite similar to e.g. commit b3bbfb3fb5d25776b8e3f361d2eedaabb0b496cd > > x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec > > in scope. > > > > That one doesn't seem to be tagged for stable. Was it queued > > there in practice? > > not marked for stable but it went in. At least to 4.4. So I guess the answer is I don't know. If you feel it's justified, then sure, feel free to forward. -- MST