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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 37E81C43462 for ; Mon, 26 Apr 2021 19:29:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11364611ED for ; Mon, 26 Apr 2021 19:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240340AbhDZTaW convert rfc822-to-8bit (ORCPT ); Mon, 26 Apr 2021 15:30:22 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35353 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240318AbhDZTaO (ORCPT ); Mon, 26 Apr 2021 15:30:14 -0400 Received: from 1.general.jvosburgh.us.vpn ([10.172.68.206] helo=famine.localdomain) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lb6v6-0000rS-DQ; Mon, 26 Apr 2021 19:29:24 +0000 Received: by famine.localdomain (Postfix, from userid 1000) id CA5CC5FDD5; Mon, 26 Apr 2021 12:29:22 -0700 (PDT) Received: from famine (localhost [127.0.0.1]) by famine.localdomain (Postfix) with ESMTP id C275E9FC56; Mon, 26 Apr 2021 12:29:22 -0700 (PDT) From: Jay Vosburgh To: David Miller cc: jinyiting@huawei.com, vfalico@gmail.com, andy@greyhouse.net, kuba@kernel.org, netdev@vger.kernel.org, security@kernel.org, linux-kernel@vger.kernel.org, xuhanbing@huawei.com, wangxiaogang3@huawei.com Subject: Re: [PATCH] bonding: 3ad: Fix the conflict between bond_update_slave_arr and the state machine In-reply-to: <20210426.120822.232032630973964712.davem@davemloft.net> References: <1618994301-1186-1-git-send-email-jinyiting@huawei.com> <20210423.130748.1071901004935481894.davem@davemloft.net> <20034.1619450557@famine> <20210426.120822.232032630973964712.davem@davemloft.net> Comments: In-reply-to David Miller message dated "Mon, 26 Apr 2021 12:08:22 -0700." X-Mailer: MH-E 8.6+git; nmh 1.6; GNU Emacs 27.0.50 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Date: Mon, 26 Apr 2021 12:29:22 -0700 Message-ID: <31539.1619465362@famine> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Miller wrote: >From: Jay Vosburgh >Date: Mon, 26 Apr 2021 08:22:37 -0700 > >> David Miller wrote: >> >>>From: jinyiting >>>Date: Wed, 21 Apr 2021 16:38:21 +0800 >>> >>>> The bond works in mode 4, and performs down/up operations on the bond >>>> that is normally negotiated. The probability of bond-> slave_arr is NULL >>>> >>>> Test commands: >>>> ifconfig bond1 down >>>> ifconfig bond1 up >>>> >>>> The conflict occurs in the following process： >>>> >>>> __dev_open (CPU A) >>>> --bond_open >>>> --queue_delayed_work(bond->wq,&bond->ad_work,0); >>>> --bond_update_slave_arr >>>> --bond_3ad_get_active_agg_info >>>> >>>> ad_work(CPU B) >>>> --bond_3ad_state_machine_handler >>>> --ad_agg_selection_logic >>>> >>>> ad_work runs on cpu B. In the function ad_agg_selection_logic, all >>>> agg->is_active will be cleared. Before the new active aggregator is >>>> selected on CPU B, bond_3ad_get_active_agg_info failed on CPU A, >>>> bond->slave_arr will be set to NULL. The best aggregator in >>>> ad_agg_selection_logic has not changed, no need to update slave arr. >>>> >>>> The conflict occurred in that ad_agg_selection_logic clears >>>> agg->is_active under mode_lock, but bond_open -> bond_update_slave_arr >>>> is inspecting agg->is_active outside the lock. >>>> >>>> Also, bond_update_slave_arr is normal for potential sleep when >>>> allocating memory, so replace the WARN_ON with a call to might_sleep. >>>> >>>> Signed-off-by: jinyiting >>>> --- >>>> >>>> Previous versions: >>>> * https://lore.kernel.org/netdev/612b5e32-ea11-428e-0c17-e2977185f045@huawei.com/ >>>> >>>> drivers/net/bonding/bond_main.c | 7 ++++--- >>>> 1 file changed, 4 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c >>>> index 74cbbb2..83ef62d 100644 >>>> --- a/drivers/net/bonding/bond_main.c >>>> +++ b/drivers/net/bonding/bond_main.c >>>> @@ -4406,7 +4404,9 @@ int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave) >>>> if (BOND_MODE(bond) == BOND_MODE_8023AD) { >>>> struct ad_info ad_info; >>>> >>>> + spin_lock_bh(&bond->mode_lock); >>> >>>The code paths that call this function with mode_lock held will now deadlock. >> >> No path should be calling bond_update_slave_arr with mode_lock >> already held (it expects RTNL only); did you find one? >> >> My concern is that there's something else that does the opposite >> order, i.e., mode_lock first, then RTNL, but I haven't found an example. >> > >This patch is removing a lockdep assertion masking sure that mode_lock was held >when this function was called. That should have been triggering all the time, right? The line in question is: #ifdef CONFIG_LOCKDEP WARN_ON(lockdep_is_held(&bond->mode_lock)); #endif The WARN_ON is triggering if mode_lock is held, not asserting that mode_lock is held. I think that's wrong anyway, since mode_lock could be held by some other thread, leading to false positives, thus the change to might_sleep. -J --- -Jay Vosburgh, jay.vosburgh@canonical.com