From: Jay Vosburgh <jay.vosburgh@canonical.com>

Date: Tue, 7 Nov 2017 19:50:07 +0900

Subject: bonding: fix slave stuck in BOND_LINK_FAIL state

Git-commit: 055db6957e4735b16cd2fa94a5bbfb754c9b8023

Patch-mainline: 4.14

References: networking-stable-19_11_10

The bonding miimon logic has a flaw, in that a failure of the

rtnl_trylock can cause a slave to become permanently stuck in

BOND_LINK_FAIL state.

	The sequence of events to cause this is as follows:

	1) bond_miimon_inspect finds that a slave's link is down, and so

calls bond_propose_link_state, setting slave->new_link_state to

BOND_LINK_FAIL, then sets slave->new_link to BOND_LINK_DOWN and returns

non-zero.

	2) In bond_mii_monitor, the rtnl_trylock fails, and the timer is

rescheduled.  No change is committed.

	3) bond_miimon_inspect is called again, but this time the slave

from step 1 has recovered.  slave->new_link is reset to NOCHANGE, and, as

slave->link was never changed, the switch enters the BOND_LINK_UP case,

and does nothing.  The pending BOND_LINK_FAIL state from step 1 remains

pending, as new_link_state is not reset.

	4) The state from step 3 persists until another slave changes link

state and causes bond_miimon_inspect to return non-zero.  At this point,

the BOND_LINK_FAIL state change on the slave from steps 1-3 is committed,

and the slave will remain stuck in BOND_LINK_FAIL state even though it

is actually link up.

	The remedy for this is to initialize new_link_state on each entry

to bond_miimon_inspect, as is already done with new_link.

Fixes: fb9eb899a6dc ("bonding: handle link transition from FAIL to UP correctly")

Reported-by: Alex Sidorenko <alexandre.sidorenko@hpe.com>

Reviewed-by: Jarod Wilson <jarod@redhat.com>

Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>

Acked-by: Mahesh Bandewar <maheshb@google.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 drivers/net/bonding/bond_main.c |    1 +

 1 file changed, 1 insertion(+)

--- a/drivers/net/bonding/bond_main.c

+++ b/drivers/net/bonding/bond_main.c

@@ -2039,6 +2039,7 @@ static int bond_miimon_inspect(struct bo

 	bond_for_each_slave_rcu(bond, slave, iter) {

 		slave->new_link = BOND_LINK_NOCHANGE;

+		slave->link_new_state = slave->link;

 		link_state = bond_check_dev_link(bond, slave->dev, 0);