This is a note to let you know that I've just added the patch titled bonding: Don't update slave->link until ready to commit to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bonding-don-t-update-slave-link-until-ready-to-commit.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Tue Apr 10 10:31:53 CEST 2018 From: Nithin Sujir <nsujir@xxxxxxxxxx> Date: Wed, 24 May 2017 19:45:17 -0700 Subject: bonding: Don't update slave->link until ready to commit From: Nithin Sujir <nsujir@xxxxxxxxxx> [ 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 <nsujir@xxxxxxxxxx> Cc: Mahesh Bandewar <maheshb@xxxxxxxxxx> Cc: Jay Vosburgh <jay.vosburgh@xxxxxxxxxxxxx> Acked-by: Mahesh Bandewar <maheshb@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -2555,11 +2555,13 @@ 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 @@ -2586,7 +2588,7 @@ 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) @@ -2617,6 +2619,11 @@ 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) Patches currently in stable-queue which might be from nsujir@xxxxxxxxxx are queue-4.4/bonding-don-t-update-slave-link-until-ready-to-commit.patch