From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36322 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754476AbeDKS5a (ORCPT ); Wed, 11 Apr 2018 14:57:30 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nithin Nayak Sujir , Mahesh Bandewar , Jay Vosburgh , "David S. Miller" , Sasha Levin Subject: [PATCH 4.9 112/310] bonding: Dont update slave->link until ready to commit Date: Wed, 11 Apr 2018 20:34:11 +0200 Message-Id: <20180411183627.007204341@linuxfoundation.org> In-Reply-To: <20180411183622.305902791@linuxfoundation.org> References: <20180411183622.305902791@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nithin Sujir [ Upstream commit 797a93647a48d6cb8a20641a86a71713a947f786 ] In the loadbalance arp monitoring scheme, when a slave link change is detected, the slave->link is immediately updated and slave_state_changed is set. Later down the function, the rtnl_lock is acquired and the changes are committed, updating the bond link state. However, the acquisition of the rtnl_lock can fail. The next time the monitor runs, since slave->link is already updated, it determines that link is unchanged. This results in the bond link state permanently out of sync with the slave link. This patch modifies bond_loadbalance_arp_mon() to handle link changes identical to bond_ab_arp_{inspect/commit}(). The new link state is maintained in slave->new_link until we're ready to commit at which point it's copied into slave->link. NOTE: miimon_{inspect/commit}() has a more complex state machine requiring the use of the bond_{propose,commit}_link_state() functions which maintains the intermediate state in slave->link_new_state. The arp monitors don't require that. Testing: This bug is very easy to reproduce with the following steps. 1. In a loop, toggle a slave link of a bond slave interface. 2. In a separate loop, do ifconfig up/down of an unrelated interface to create contention for rtnl_lock. Within a few iterations, the bond link goes out of sync with the slave link. Signed-off-by: Nithin Nayak Sujir Cc: Mahesh Bandewar Cc: Jay Vosburgh Acked-by: Mahesh Bandewar Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/bonding/bond_main.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2605,11 +2605,13 @@ static void bond_loadbalance_arp_mon(str bond_for_each_slave_rcu(bond, slave, iter) { unsigned long trans_start = dev_trans_start(slave->dev); + slave->new_link = BOND_LINK_NOCHANGE; + if (slave->link != BOND_LINK_UP) { if (bond_time_in_interval(bond, trans_start, 1) && bond_time_in_interval(bond, slave->last_rx, 1)) { - slave->link = BOND_LINK_UP; + slave->new_link = BOND_LINK_UP; slave_state_changed = 1; /* primary_slave has no meaning in round-robin @@ -2636,7 +2638,7 @@ static void bond_loadbalance_arp_mon(str if (!bond_time_in_interval(bond, trans_start, 2) || !bond_time_in_interval(bond, slave->last_rx, 2)) { - slave->link = BOND_LINK_DOWN; + slave->new_link = BOND_LINK_DOWN; slave_state_changed = 1; if (slave->link_failure_count < UINT_MAX) @@ -2667,6 +2669,11 @@ static void bond_loadbalance_arp_mon(str if (!rtnl_trylock()) goto re_arm; + bond_for_each_slave(bond, slave, iter) { + if (slave->new_link != BOND_LINK_NOCHANGE) + slave->link = slave->new_link; + } + if (slave_state_changed) { bond_slave_state_change(bond); if (BOND_MODE(bond) == BOND_MODE_XOR)