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,URIBL_BLOCKED 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 DA399C004C9 for ; Thu, 9 May 2019 03:20:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADA1D216C4 for ; Thu, 9 May 2019 03:20:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726791AbfEIDU1 (ORCPT ); Wed, 8 May 2019 23:20:27 -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 S1726251AbfEIDUZ (ORCPT ); Wed, 8 May 2019 23:20:25 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 69F688665F; Thu, 9 May 2019 03:20:25 +0000 (UTC) Received: from hp-dl380pg8-02.lab.eng.pek2.redhat.com (hp-dl380pg8-02.lab.eng.pek2.redhat.com [10.73.8.12]) by smtp.corp.redhat.com (Postfix) with ESMTP id 48A355C221; Thu, 9 May 2019 03:20:23 +0000 (UTC) From: Jason Wang To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: yuehaibing@huawei.com, xiyou.wangcong@gmail.com, weiyongjun1@huawei.com, eric.dumazet@gmail.com, Jason Wang Subject: [PATCH net V3 2/2] tuntap: synchronize through tfiles array instead of tun->numqueues Date: Wed, 8 May 2019 23:20:18 -0400 Message-Id: <1557372018-18544-2-git-send-email-jasowang@redhat.com> In-Reply-To: <1557372018-18544-1-git-send-email-jasowang@redhat.com> References: <1557372018-18544-1-git-send-email-jasowang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 09 May 2019 03:20:25 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a queue(tfile) is detached through __tun_detach(), we move the last enabled tfile to the position where detached one sit but don't NULL out last position. We expect to synchronize the datapath through tun->numqueues. Unfortunately, this won't work since we're lacking sufficient mechanism to order or synchronize the access to tun->numqueues. To fix this, NULL out the last position during detaching and check RCU protected tfile against NULL instead of checking tun->numqueues in datapath. Cc: YueHaibing Cc: Cong Wang Cc: weiyongjun (A) Cc: Eric Dumazet Fixes: c8d68e6be1c3b ("tuntap: multiqueue support") Signed-off-by: Jason Wang --- Changes from V2: - resample during detach in tun_xdp_xmit() Changes from V1: - keep the check in tun_xdp_xmit() --- drivers/net/tun.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index dc62fc3..f4c933a 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -705,6 +705,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->tfiles[tun->numqueues - 1]); ntfile = rtnl_dereference(tun->tfiles[index]); ntfile->queue_index = index; + rcu_assign_pointer(tun->tfiles[tun->numqueues - 1], + NULL); --tun->numqueues; if (clean) { @@ -1087,7 +1089,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) tfile = rcu_dereference(tun->tfiles[txq]); /* Drop packet if interface is not attached */ - if (txq >= tun->numqueues) + if (!tfile) goto drop; if (!rcu_dereference(tun->steering_prog)) @@ -1310,6 +1312,7 @@ static int tun_xdp_xmit(struct net_device *dev, int n, rcu_read_lock(); +resample: numqueues = READ_ONCE(tun->numqueues); if (!numqueues) { rcu_read_unlock(); @@ -1318,6 +1321,8 @@ static int tun_xdp_xmit(struct net_device *dev, int n, tfile = rcu_dereference(tun->tfiles[smp_processor_id() % numqueues]); + if (unlikely(!tfile)) + goto resample; spin_lock(&tfile->tx_ring.producer_lock); for (i = 0; i < n; i++) { -- 1.8.3.1