net/bonding: Fix potential bad memory access during bonding events

When queuing work to send the NETDEV_BONDING_INFO netdev event, it's
possible that when the work is executed, the pointer to the slave
becomes invalid. This can happen if between queuing the event and the
execution of the work, the net-device was un-ensvaled and re-enslaved.

Fix that by queuing a work with the data of the slave instead of the
slave structure.

Fixes: 69e6113 ('net/bonding: Notify state change on slaves')
Reported-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1196,18 +1196,11 @@ static void bond_fill_ifslave(struct slave *slave, struct ifslave *info)
 	info->link_failure_count = slave->link_failure_count;
 }
 
-static void bond_netdev_notify(struct slave *slave, struct net_device *dev)
+static void bond_netdev_notify(struct net_device *dev,
+			       struct netdev_bonding_info *info)
 {
-	struct bonding *bond = slave->bond;
-	struct netdev_bonding_info bonding_info;
-
 	rtnl_lock();
-	/* make sure that slave is still valid */
-	if (dev->priv_flags & IFF_BONDING) {
-		bond_fill_ifslave(slave, &bonding_info.slave);
-		bond_fill_ifbond(bond, &bonding_info.master);
-		netdev_bonding_info_change(slave->dev, &bonding_info);
-	}
+	netdev_bonding_info_change(dev, info);
 	rtnl_unlock();
 }
 
@@ -1216,25 +1209,26 @@ static void bond_netdev_notify_work(struct work_struct *_work)
 	struct netdev_notify_work *w =
 		container_of(_work, struct netdev_notify_work, work.work);
 
-	bond_netdev_notify(w->slave, w->dev);
+	bond_netdev_notify(w->dev, &w->bonding_info);
 	dev_put(w->dev);
+	kfree(w);
 }
 
 void bond_queue_slave_event(struct slave *slave)
 {
+	struct bonding *bond = slave->bond;
 	struct netdev_notify_work *nnw = kzalloc(sizeof(*nnw), GFP_ATOMIC);
 
 	if (!nnw)
 		return;
 
-	INIT_DELAYED_WORK(&nnw->work, bond_netdev_notify_work);
-	nnw->slave = slave;
+	dev_hold(slave->dev);
 	nnw->dev = slave->dev;
+	bond_fill_ifslave(slave, &nnw->bonding_info.slave);
+	bond_fill_ifbond(bond, &nnw->bonding_info.master);
+	INIT_DELAYED_WORK(&nnw->work, bond_netdev_notify_work);
 
-	if (queue_delayed_work(slave->bond->wq, &nnw->work, 0))
-		dev_hold(slave->dev);
-	else
-		kfree(nnw);
+	queue_delayed_work(slave->bond->wq, &nnw->work, 0);
 }
 
 /* enslave device <slave> to bond device <master> */

include/net/bonding.h

@@ -152,8 +152,8 @@ struct bond_parm_tbl {
 
 struct netdev_notify_work {
 	struct delayed_work	work;
-	struct slave		*slave;
 	struct net_device	*dev;
+	struct netdev_bonding_info bonding_info;
 };
 
 struct slave {