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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,PDS_TONAME_EQ_TOLOCAL_HDRS_LCASE,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 D665FC433ED for ; Fri, 16 Apr 2021 04:28:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7CD5611BF for ; Fri, 16 Apr 2021 04:28:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238118AbhDPE3F convert rfc822-to-8bit (ORCPT ); Fri, 16 Apr 2021 00:29:05 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:49211 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236800AbhDPE3A (ORCPT ); Fri, 16 Apr 2021 00:29:00 -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 1lXG5l-0002WV-3G; Fri, 16 Apr 2021 04:28:29 +0000 Received: by famine.localdomain (Postfix, from userid 1000) id 2C5D261DE4; Thu, 15 Apr 2021 21:28:27 -0700 (PDT) Received: from famine (localhost [127.0.0.1]) by famine.localdomain (Postfix) with ESMTP id 2543EA040D; Thu, 15 Apr 2021 21:28:27 -0700 (PDT) From: Jay Vosburgh To: jinyiting cc: vfalico@gmail.com, andy@greyhouse.net, davem@davemloft.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: update slave arr after initialize In-reply-to: <1618537982-454-1-git-send-email-jinyiting@huawei.com> References: <1618537982-454-1-git-send-email-jinyiting@huawei.com> Comments: In-reply-to jinyiting message dated "Fri, 16 Apr 2021 09:53:02 +0800." 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: Thu, 15 Apr 2021 21:28:27 -0700 Message-ID: <17733.1618547307@famine> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org jinyiting wrote: >From: jin yiting > >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. > >Signed-off-by: jin yiting >--- > drivers/net/bonding/bond_3ad.c | 6 ++++++ > 1 file changed, 6 insertions(+) > >diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c >index 6908822..d100079 100644 >--- a/drivers/net/bonding/bond_3ad.c >+++ b/drivers/net/bonding/bond_3ad.c >@@ -2327,6 +2327,12 @@ void bond_3ad_state_machine_handler(struct work_struct *work) > > aggregator = __get_first_agg(port); > ad_agg_selection_logic(aggregator, &update_slave_arr); >+ if (!update_slave_arr) { >+ struct aggregator *active = __get_active_agg(aggregator); >+ >+ if (active && active->is_active) >+ update_slave_arr = true; >+ } > } > bond_3ad_set_carrier(bond); > } The described issue is a race condition (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). I don't see how the above change will reliably manage this; the real issue looks to be that bond_update_slave_arr is committing changes to the array (via bond_reset_slave_arr) based on a racy inspection of the active aggregator state while it is in flux. Also, the description of the issue says "The best aggregator in ad_agg_selection_logic has not changed, no need to update slave arr," but the change above does the opposite, and will set update_slave_arr when the aggregator has not changed (update_slave_arr remains false at return of ad_agg_selection_logic). I believe I understand the described problem, but I don't see how the patch fixes it. I suspect (but haven't tested) that the proper fix is to acquire mode_lock in bond_update_slave_arr while calling bond_3ad_get_active_agg_info to avoid conflict with the state machine. -J --- -Jay Vosburgh, jay.vosburgh@canonical.com