leds: trigger: netdev: Fix kernel panic on interface rename trig notify

[ Upstream commit 415798b ]

Commit d5e0126 ("leds: trigger: netdev: add additional specific link
speed mode") in the various changes, reworked the way to set the LINKUP
mode in commit cee4bd1 ("leds: trigger: netdev: Recheck
NETDEV_LED_MODE_LINKUP on dev rename") and moved it to a generic function.

This changed the logic where, in the previous implementation the dev
from the trigger event was used to check if the carrier was ok, but in
the new implementation with the generic function, the dev in
trigger_data is used instead.

This is problematic and cause a possible kernel panic due to the fact
that the dev in the trigger_data still reference the old one as the
new one (passed from the trigger event) still has to be hold and saved
in the trigger_data struct (done in the NETDEV_REGISTER case).

On calling of get_device_state(), an invalid net_dev is used and this
cause a kernel panic.

To handle this correctly, move the call to get_device_state() after the
new net_dev is correctly set in trigger_data (in the NETDEV_REGISTER
case) and correctly parse the new dev.

Fixes: d5e0126 ("leds: trigger: netdev: add additional specific link speed mode")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240203235413.1146-1-ansuelsmth@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/leds/trigger/ledtrig-netdev.c

@@ -462,12 +462,12 @@ static int netdev_trig_notify(struct notifier_block *nb,
 	trigger_data->duplex = DUPLEX_UNKNOWN;
 	switch (evt) {
 	case NETDEV_CHANGENAME:
-		get_device_state(trigger_data);
-		fallthrough;
 	case NETDEV_REGISTER:
 		dev_put(trigger_data->net_dev);
 		dev_hold(dev);
 		trigger_data->net_dev = dev;
+		if (evt == NETDEV_CHANGENAME)
+			get_device_state(trigger_data);
 		break;
 	case NETDEV_UNREGISTER:
 		dev_put(trigger_data->net_dev);