netdev - [PATCH] bonding: Fix race condition between bond_enslave() and bond_3ad_update_lacp

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Date:	Mon, 18 Feb 2013 13:45:30 +0100
From:	Nikolay Aleksandrov <nikolay@...hat.com>
To:	netdev@...r.kernel.org
Cc:	andy@...yhouse.net, fubar@...ibm.com, davem@...emloft.net
Subject: [PATCH] bonding: Fix race condition between bond_enslave() and bond_3ad_update_lacp_rate()

port->slave can be NULL since it's being initialized in bond_enslave
thus dereferencing a NULL pointer in bond_3ad_update_lacp_rate()
Also fix a minor bug, which could cause a port not to have
AD_STATE_LACP_TIMEOUT since there's no sync between
bond_3ad_update_lacp_rate() and bond_3ad_bind_slave(), by changing
the read_lock to a write_lock_bh in bond_3ad_update_lacp_rate().

Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>
---
 drivers/net/bonding/bond_3ad.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index a030e63..1720742 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2494,11 +2494,13 @@ void bond_3ad_update_lacp_rate(struct bonding *bond)
 	struct port *port = NULL;
 	int lacp_fast;
 
-	read_lock(&bond->lock);
+	write_lock_bh(&bond->lock);
 	lacp_fast = bond->params.lacp_fast;
 
 	bond_for_each_slave(bond, slave, i) {
 		port = &(SLAVE_AD_INFO(slave).port);
+		if (port->slave == NULL)
+			continue;
 		__get_state_machine_lock(port);
 		if (lacp_fast)
 			port->actor_oper_port_state |= AD_STATE_LACP_TIMEOUT;
@@ -2507,5 +2509,5 @@ void bond_3ad_update_lacp_rate(struct bonding *bond)
 		__release_state_machine_lock(port);
 	}
 
-	read_unlock(&bond->lock);
+	write_unlock_bh(&bond->lock);
 }
-- 
1.7.11.7

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