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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 4E3F1C43461 for ; Fri, 11 Sep 2020 14:35:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01F982226B for ; Fri, 11 Sep 2020 14:35:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599834949; bh=g0Tx0buTZ4v0lJqs0QvuGVYtuk5Alm9+RarIUFQmvcE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Vcz00gxjLUwdHnje7L675opKrd2G3zcTrgi51nVOc0AaJIJc9X/wRhHjCFZgId4yT n5DwbktgxF69DYpVxqLTdjY8/PoR+35J2GFa5vJEtAU9TFDW5NxIF7HdreF7w1LuDQ Mb+up2HL0RyQ6RWV4qMRd1t8vyGycc96NxUm2y3o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726228AbgIKOfl (ORCPT ); Fri, 11 Sep 2020 10:35:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:56024 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726155AbgIKNMA (ORCPT ); Fri, 11 Sep 2020 09:12:00 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 23A5C206A2; Fri, 11 Sep 2020 13:00:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599829230; bh=g0Tx0buTZ4v0lJqs0QvuGVYtuk5Alm9+RarIUFQmvcE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w3TMX521c81c76BBehZVa/HNZ81mxkJIEWjhaqdiW20s9E7pgkxlqiv8Dh2lNrERw 2wO/gCCjUm243s56tGE8j06gyttMym/Y+X+wOdaL6ZnC5SQR4FW71+VV8PjpciB/L+ zMZ0w4JRgKgiW3jdNQnA9t9Sohh7PR6mF4SQZrp8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rob Sherwood , Jakub Kicinski , "David S. Miller" Subject: [PATCH 5.4 8/8] net: disable netpoll on fresh napis Date: Fri, 11 Sep 2020 14:54:46 +0200 Message-Id: <20200911125420.968741538@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200911125420.580564179@linuxfoundation.org> References: <20200911125420.580564179@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jakub Kicinski [ Upstream commit 96e97bc07e90f175a8980a22827faf702ca4cb30 ] napi_disable() makes sure to set the NAPI_STATE_NPSVC bit to prevent netpoll from accessing rings before init is complete. However, the same is not done for fresh napi instances in netif_napi_add(), even though we expect NAPI instances to be added as disabled. This causes crashes during driver reconfiguration (enabling XDP, changing the channel count) - if there is any printk() after netif_napi_add() but before napi_enable(). To ensure memory ordering is correct we need to use RCU accessors. Reported-by: Rob Sherwood Fixes: 2d8bff12699a ("netpoll: Close race condition between poll_one_napi and napi_disable") Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/dev.c | 3 ++- net/core/netpoll.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6231,12 +6231,13 @@ void netif_napi_add(struct net_device *d netdev_err_once(dev, "%s() called with weight %d\n", __func__, weight); napi->weight = weight; - list_add(&napi->dev_list, &dev->napi_list); napi->dev = dev; #ifdef CONFIG_NETPOLL napi->poll_owner = -1; #endif set_bit(NAPI_STATE_SCHED, &napi->state); + set_bit(NAPI_STATE_NPSVC, &napi->state); + list_add_rcu(&napi->dev_list, &dev->napi_list); napi_hash_add(napi); } EXPORT_SYMBOL(netif_napi_add); --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -161,7 +161,7 @@ static void poll_napi(struct net_device struct napi_struct *napi; int cpu = smp_processor_id(); - list_for_each_entry(napi, &dev->napi_list, dev_list) { + list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) { if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) { poll_one_napi(napi); smp_store_release(&napi->poll_owner, -1);