kernel: fix refcnt leak in LED netdev trigger on interface rename

Renaming a netdev-trigger-tracked interface was resulting in an
unbalanced dev_hold().

Example:
> iw phy phy0 interface add foo type __ap
> echo netdev > trigger
> echo foo > device_name
> ip link set foo name bar
> iw dev bar del
[  237.355366] unregister_netdevice: waiting for bar to become free. Usage count = 1
[  247.435362] unregister_netdevice: waiting for bar to become free. Usage count = 1
[  257.545366] unregister_netdevice: waiting for bar to become free. Usage count = 1

Above problem was caused by trigger checking a dev->name which obviously
changes after renaming an interface. It meant missing all further events
including the NETDEV_UNREGISTER which is required for calling dev_put().

This change fixes that by:
1) Comparing device struct *address* for notification-filtering purposes
2) Dropping unneeded NETDEV_CHANGENAME code (no behavior change)

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit eea538204bb973d73d3bc3d38947d7f85214d486)

diff --git a/target/linux/generic/files/drivers/leds/ledtrig-netdev.c b/target/linux/generic/files/drivers/leds/ledtrig-netdev.c
index 7246bcaf7e7b91029fa00bc25d8130a1ae95a043..2d83541fef59ddf0fb5be3e8993d1445557e3046 100644 (file)
--- a/target/linux/generic/files/drivers/leds/ledtrig-netdev.c
+++ b/target/linux/generic/files/drivers/leds/ledtrig-netdev.c
@@ -264,39 +264,35 @@ static int netdev_trig_notify(struct notifier_block *nb,
        struct net_device *dev = netdev_notifier_info_to_dev((struct netdev_notifier_info *) dv);
        struct led_netdev_data *trigger_data = container_of(nb, struct led_netdev_data, notifier);
 
-       if (evt != NETDEV_UP && evt != NETDEV_DOWN && evt != NETDEV_CHANGE && evt != NETDEV_REGISTER && evt != NETDEV_UNREGISTER && evt != NETDEV_CHANGENAME)
+       if (evt != NETDEV_UP && evt != NETDEV_DOWN && evt != NETDEV_CHANGE && evt != NETDEV_REGISTER && evt != NETDEV_UNREGISTER)
                return NOTIFY_DONE;
 
-       if (strcmp(dev->name, trigger_data->device_name))
+       if (!(dev == trigger_data->net_dev ||
+             (evt == NETDEV_REGISTER && !strcmp(dev->name, trigger_data->device_name))))
                return NOTIFY_DONE;
 
        cancel_delayed_work_sync(&trigger_data->work);
 
        spin_lock_bh(&trigger_data->lock);
 
-       if (evt == NETDEV_REGISTER || evt == NETDEV_CHANGENAME) {
-               if (trigger_data->net_dev != NULL)
-                       dev_put(trigger_data->net_dev);
-
+       switch (evt) {
+       case NETDEV_REGISTER:
                dev_hold(dev);
                trigger_data->net_dev = dev;
                trigger_data->link_up = 0;
-               goto done;
-       }
-
-       if (evt == NETDEV_UNREGISTER && trigger_data->net_dev != NULL) {
+               break;
+       case NETDEV_UNREGISTER:
                dev_put(trigger_data->net_dev);
                trigger_data->net_dev = NULL;
-               goto done;
+               break;
+       default: /* UP / DOWN / CHANGE */
+               trigger_data->link_up = (evt != NETDEV_DOWN && netif_carrier_ok(dev));
+               set_baseline_state(trigger_data);
+               break;
        }
 
-       /* UP / DOWN / CHANGE */
-
-       trigger_data->link_up = (evt != NETDEV_DOWN && netif_carrier_ok(dev));
-       set_baseline_state(trigger_data);
-
-done:
        spin_unlock_bh(&trigger_data->lock);
+
        return NOTIFY_DONE;
 }