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

This fixes a possible unbalanced dev_hold():
> 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

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

1 files changed, 69 insertions, 0 deletions

diff --git a/target/linux/generic/backport-4.14/401-v5.2-leds-trigger-netdev-fix-refcnt-leak-on-interface-ren.patch b/target/linux/generic/backport-4.14/401-v5.2-leds-trigger-netdev-fix-refcnt-leak-on-interface-ren.patch
new file mode 100644
index 0000000000..32682627fc
--- /dev/null
+++ b/target/linux/generic/backport-4.14/401-v5.2-leds-trigger-netdev-fix-refcnt-leak-on-interface-ren.patch
@@ -0,0 +1,69 @@
+From dd7590a3ab3f0804ed5e930295e2caa5979e3958 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Thu, 28 Feb 2019 22:57:33 +0100
+Subject: [PATCH] leds: trigger: netdev: fix refcnt leak on interface rename
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+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>
+---
+ drivers/leds/trigger/ledtrig-netdev.c | 13 +++++--------
+ 1 file changed, 5 insertions(+), 8 deletions(-)
+
+--- a/drivers/leds/trigger/ledtrig-netdev.c
++++ b/drivers/leds/trigger/ledtrig-netdev.c
+@@ -299,11 +299,11 @@ static int netdev_trig_notify(struct not
+ 							    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);
+@@ -318,12 +318,9 @@ static int netdev_trig_notify(struct not
+ 		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: