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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3800C32774 for ; Mon, 22 Aug 2022 01:39:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232298AbiHVBj2 (ORCPT ); Sun, 21 Aug 2022 21:39:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230094AbiHVBjZ (ORCPT ); Sun, 21 Aug 2022 21:39:25 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 933662127A; Sun, 21 Aug 2022 18:39:24 -0700 (PDT) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4M9w175Wqnz1N7R0; Mon, 22 Aug 2022 09:35:55 +0800 (CST) Received: from dggpemm500007.china.huawei.com (7.185.36.183) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 22 Aug 2022 09:39:22 +0800 Received: from [10.174.178.174] (10.174.178.174) by dggpemm500007.china.huawei.com (7.185.36.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 22 Aug 2022 09:39:22 +0800 Subject: Re: [PATCH net v2] net: neigh: don't call kfree_skb() under spin_lock_irqsave() To: Nikolay Aleksandrov , , CC: , , , References: <20220819044724.961356-1-yangyingliang@huawei.com> From: Yang Yingliang Message-ID: Date: Mon, 22 Aug 2022 09:39:21 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.178.174] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500007.china.huawei.com (7.185.36.183) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2022/8/19 20:15, Nikolay Aleksandrov wrote: > On 19/08/2022 07:47, Yang Yingliang wrote: >> It is not allowed to call kfree_skb() from hardware interrupt >> context or with interrupts being disabled. So add all skb to >> a tmp list, then free them after spin_unlock_irqrestore() at >> once. >> >> Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop") >> Signed-off-by: Yang Yingliang >> --- >> net/core/neighbour.c | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/net/core/neighbour.c b/net/core/neighbour.c >> index 5b669eb80270..d21c7de1ff1a 100644 >> --- a/net/core/neighbour.c >> +++ b/net/core/neighbour.c >> @@ -309,14 +309,17 @@ static int neigh_del_timer(struct neighbour *n) >> >> static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net) >> { >> + struct sk_buff_head tmp; >> unsigned long flags; >> struct sk_buff *skb; >> >> + skb_queue_head_init(&tmp); >> spin_lock_irqsave(&list->lock, flags); >> skb = skb_peek(list); >> while (skb != NULL) { >> struct sk_buff *skb_next = skb_peek_next(skb, list); >> struct net_device *dev = skb->dev; >> + >> if (net == NULL || net_eq(dev_net(dev), net)) { >> struct in_device *in_dev; >> >> @@ -328,11 +331,16 @@ static void :q > (struct sk_buff_head *list, struct net *net) >> __skb_unlink(skb, list); >> >> dev_put(dev); >> - kfree_skb(skb); >> + dev_kfree_skb_irq(skb); > this is still doing dev_kfree_skb_irq() instead of attaching the skb to tmp, in fact > tmp seems unused so the loop below does nothing > >> } >> skb = skb_next; >> } >> spin_unlock_irqrestore(&list->lock, flags); >> + >> + while ((skb = __skb_dequeue(&tmp))) { >> + dev_put(skb->dev); > Also note that there's already a dev_put() above I made a mistake and send a wrong patch, please ignore this patch. Thanks, Yang > >> + kfree_skb(skb); >> + } >> } >> >> static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev, > > .