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Subject[PATCH AUTOSEL 4.19 53/68] leds: trigger: netdev: fix refcnt leak on interface rename
Date
From: Rafał Miłecki <rafal@milecki.pl>

[ Upstream commit 4cb6560514fa19d556954b88128f3846fee66a03 ]

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)

Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
---
drivers/leds/trigger/ledtrig-netdev.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 3dd3ed46d473..167a94c02d05 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -301,11 +301,11 @@ static int netdev_trig_notify(struct notifier_block *nb,
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)
+ && 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);
@@ -320,12 +320,9 @@ static int netdev_trig_notify(struct notifier_block *nb,
dev_hold(dev);
trigger_data->net_dev = dev;
break;
- case NETDEV_CHANGENAME:
case NETDEV_UNREGISTER:
- if (trigger_data->net_dev) {
- dev_put(trigger_data->net_dev);
- trigger_data->net_dev = NULL;
- }
+ dev_put(trigger_data->net_dev);
+ trigger_data->net_dev = NULL;
break;
case NETDEV_UP:
case NETDEV_CHANGE:
--
2.19.1
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