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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 CE71DC49ED6 for ; Wed, 11 Sep 2019 12:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD0982084F for ; Wed, 11 Sep 2019 12:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727786AbfIKMZK (ORCPT ); Wed, 11 Sep 2019 08:25:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60772 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726341AbfIKMZK (ORCPT ); Wed, 11 Sep 2019 08:25:10 -0400 Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) (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 2A1E93E2D3 for ; Wed, 11 Sep 2019 12:25:10 +0000 (UTC) Received: by mail-qt1-f198.google.com with SMTP id o1so23597970qtp.3 for ; Wed, 11 Sep 2019 05:25:10 -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=hxqdd7sLD0IIJEG1yv3oLsELLYkxr9dTgSFMh9qjyAM=; b=OKP1ie/plc0vtWmUT8GNCef/atppkpL/pNRfMfJCwNWR4F28+wvbFuw1SGON7hFpxk M0L5nzW7nRk/5/IxbTNLWRTBebqAYVzjwxVplj/7mq/uuLjZHZmzKHfQlTzuMp6o2YS1 BspoPbgqn4szXJN2cihjN+6LxU9cOcmBJhypuJ4jzDr+IDIHlaNSKy2mUz/gBRNBnI8i q5OinDpWH40wuCyUCXVwUE5h0Wrfq8KprfoPb2U2VRJOVqcR3fcvn/sQHe/gWIpUx/tR Q+rewds0ck/wk4XgGjFHLYvVBrSAd+kOGUpZyPfFepbX9bDoV2mBx0b3SoMGkUML/brz 0QRQ== X-Gm-Message-State: APjAAAUxrBHiYrAL3upff1DQyGowUMr7/pEHDVXGuGCBxrsZnIEvgz5O NRZ1qjCraI5HUx1VqOLk1q9SPKzZPtpYyHaBFnyYpdE0hCa+lCt9IIrDJozObJEoan/Ccr3cPoQ JOx7USIlQEdH4 X-Received: by 2002:a37:a858:: with SMTP id r85mr20448440qke.394.1568204709488; Wed, 11 Sep 2019 05:25:09 -0700 (PDT) X-Google-Smtp-Source: APXvYqydIpMhvodySW7CTJrCuCWEytvXXGQbmEf5VStZ8nkcJ6t3BKc9d/kPejtfhSjav5sm2yl2eg== X-Received: by 2002:a37:a858:: with SMTP id r85mr20448417qke.394.1568204709315; Wed, 11 Sep 2019 05:25:09 -0700 (PDT) Received: from redhat.com ([80.74.107.118]) by smtp.gmail.com with ESMTPSA id w126sm9508107qkd.68.2019.09.11.05.25.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Sep 2019 05:25:08 -0700 (PDT) Date: Wed, 11 Sep 2019 08:25:03 -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: <20190911082236-mutt-send-email-mst@kernel.org> References: <20190911120908.28410-1-mst@redhat.com> <20190911121628.GT4023@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190911121628.GT4023@dhcp22.suse.cz> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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? > > --- > > > > changes from v1: fix build on 32 bit > > > > drivers/vhost/vhost.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index 5dc174ac8cac..34ea219936e3 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -2071,8 +2071,10 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len, > > _iov = iov + ret; > > size = node->size - addr + node->start; > > _iov->iov_len = min((u64)len - s, size); > > - _iov->iov_base = (void __user *)(unsigned long) > > - (node->userspace_addr + addr - node->start); > > + _iov->iov_base = (void __user *) > > + ((unsigned long)node->userspace_addr + > > + array_index_nospec((unsigned long)(addr - node->start), > > + node->size)); > > s += size; > > addr += size; > > ++ret; > > -- > > MST > > -- > Michal Hocko > SUSE Labs