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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 8383CC04EB8 for ; Wed, 12 Dec 2018 14:33:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4094721104 for ; Wed, 12 Dec 2018 14:33:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4094721104 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1727657AbeLLOdj (ORCPT ); Wed, 12 Dec 2018 09:33:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726246AbeLLOdi (ORCPT ); Wed, 12 Dec 2018 09:33:38 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A0B723082E55; Wed, 12 Dec 2018 14:33:38 +0000 (UTC) Received: from redhat.com (ovpn-122-106.rdu2.redhat.com [10.10.122.106]) by smtp.corp.redhat.com (Postfix) with SMTP id 85E5D600C9; Wed, 12 Dec 2018 14:33:37 +0000 (UTC) Date: Wed, 12 Dec 2018 09:33:37 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net V2 1/4] vhost: make sure used idx is seen before log in vhost_add_used_n() Message-ID: <20181212093303-mutt-send-email-mst@kernel.org> References: <20181212100819.21295-1-jasowang@redhat.com> <20181212100819.21295-2-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181212100819.21295-2-jasowang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Wed, 12 Dec 2018 14:33:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 12, 2018 at 06:08:16PM +0800, Jason Wang wrote: > We miss a write barrier that guarantees used idx is updated and seen > before log. This will let userspace sync and copy used ring before > used idx is update. Fix this by adding a barrier before log_write(). > > Fixes: 8dd014adfea6f ("vhost-net: mergeable buffers support") > Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin also for 4.20 and seems like a stable candidate. > --- > drivers/vhost/vhost.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 6b98d8e3a5bf..5915f240275a 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2220,6 +2220,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads, > return -EFAULT; > } > if (unlikely(vq->log_used)) { > + /* Make sure used idx is seen before log. */ > + smp_wmb(); > /* Log used index update. */ > log_write(vq->log_base, > vq->log_addr + offsetof(struct vring_used, idx), > -- > 2.17.1