[PATCHv2 wireless] mac80211: stop tpt LED trigger timer before freeing trigger

[Rosen Penev <rosenp@gmail.com>]

The throughput (tpt) LED trigger timer is only stopped in
ieee80211_stop_tpt_led_trig(), which is reached via ieee80211_stop_device()
when the interface is brought down. On a hot unplug, the device is torn down
through ieee80211_unregister_hw() without ever going through
ieee80211_do_stop(), so the timer is never stopped.

ieee80211_led_exit() then frees local->tpt_led_trigger (which embeds the
timer) without cancelling it. The still-armed timer keeps firing and
dereferences the freed tpt_trig, walking local->tpt_led's LED list in
led_trigger_blink() -> led_blink_set_nosleep() on the freed rt2x00 LED class
device, causing a use-after-free page fault in interrupt context.

Call ieee80211_stop_tpt_led_trig() in ieee80211_led_exit(), before
unregistering the trigger and freeing the struct, so the timer is always
stopped and can never run after the trigger/LEDs are torn down.

Fixes: e1e540685437 ("mac80211: add throughput based LED blink trigger")
Assisted-by: opencode:hy3-free
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: move static function instead of forward declaration
 net/mac80211/led.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/net/mac80211/led.c b/net/mac80211/led.c
index b5600d223452..42dcd56eb983 100644
--- a/net/mac80211/led.c
+++ b/net/mac80211/led.c
@@ -194,6 +194,19 @@ void ieee80211_led_init(struct ieee80211_local *local)
 	}
 }
 
+static void ieee80211_stop_tpt_led_trig(struct ieee80211_local *local)
+{
+	struct tpt_led_trigger *tpt_trig = local->tpt_led_trigger;
+
+	if (!tpt_trig->running)
+		return;
+
+	tpt_trig->running = false;
+	timer_delete_sync(&tpt_trig->timer);
+
+	led_trigger_event(&local->tpt_led, LED_OFF);
+}
+
 void ieee80211_led_exit(struct ieee80211_local *local)
 {
 	if (local->radio_led.name)
@@ -206,6 +219,7 @@ void ieee80211_led_exit(struct ieee80211_local *local)
 		led_trigger_unregister(&local->rx_led);
 
 	if (local->tpt_led_trigger) {
+		ieee80211_stop_tpt_led_trig(local);
 		led_trigger_unregister(&local->tpt_led);
 		kfree(local->tpt_led_trigger);
 	}
@@ -335,19 +349,6 @@ static void ieee80211_start_tpt_led_trig(struct ieee80211_local *local)
 	mod_timer(&tpt_trig->timer, round_jiffies(jiffies + HZ));
 }
 
-static void ieee80211_stop_tpt_led_trig(struct ieee80211_local *local)
-{
-	struct tpt_led_trigger *tpt_trig = local->tpt_led_trigger;
-
-	if (!tpt_trig->running)
-		return;
-
-	tpt_trig->running = false;
-	timer_delete_sync(&tpt_trig->timer);
-
-	led_trigger_event(&local->tpt_led, LED_OFF);
-}
-
 void ieee80211_mod_tpt_led_trig(struct ieee80211_local *local,
 				unsigned int types_on, unsigned int types_off)
 {
-- 
2.55.0