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 49D42C6786C for ; Thu, 13 Dec 2018 02:53:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19CD820851 for ; Thu, 13 Dec 2018 02:53:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19CD820851 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 S1726854AbeLMCxv (ORCPT ); Wed, 12 Dec 2018 21:53:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42340 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726787AbeLMCxt (ORCPT ); Wed, 12 Dec 2018 21:53:49 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 371463DE04; Thu, 13 Dec 2018 02:53:49 +0000 (UTC) Received: from jason-ThinkPad-T450s.redhat.com (ovpn-12-167.pek2.redhat.com [10.72.12.167]) by smtp.corp.redhat.com (Postfix) with ESMTP id B33175D70A; Thu, 13 Dec 2018 02:53:46 +0000 (UTC) From: Jason Wang To: mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net V3 1/3] vhost: make sure used idx is seen before log in vhost_add_used_n() Date: Thu, 13 Dec 2018 10:53:37 +0800 Message-Id: <20181213025339.14023-2-jasowang@redhat.com> In-Reply-To: <20181213025339.14023-1-jasowang@redhat.com> References: <20181213025339.14023-1-jasowang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 13 Dec 2018 02:53:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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") Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang --- 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