[PATCH net 1/1] mac802154: fix netdev use-after-free in beacon worker

mac802154_beacon_worker() reads local->beacon_req under RCU and derives
the sub-interface from the request, but then drops the RCU read lock and
continues to use both sdata and the embedded wpan_dev.

mac802154_stop_beacons_locked() cancels only pending beacon work, clears
local->beacon_req and frees the request.  A beacon worker that is already
running can therefore continue after interface teardown and dereference
the freed netdev private area.

The scan worker already pins the netdev before leaving RCU.  Apply the
same lifetime rule to the beacon worker: take a netdev reference while
the request is still protected by RCU, and release it on all paths that
continue after the reference is acquired.

Fixes: 3accf4762734 ("mac802154: Handle basic beaconing")
Cc: [email protected]
Reported-by: Vega <[email protected]>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Zihan Xi <[email protected]>
---
 net/mac802154/scan.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c
index 65089826f..ebd092d40 100644
--- a/net/mac802154/scan.c
+++ b/net/mac802154/scan.c
@@ -416,6 +416,7 @@ void mac802154_beacon_worker(struct work_struct *work)
 	struct cfg802154_beacon_request *beacon_req;
 	struct ieee802154_sub_if_data *sdata;
 	struct wpan_dev *wpan_dev;
+	netdevice_tracker dev_tracker;
 	u8 interval;
 	int ret;
 
@@ -427,12 +428,14 @@ void mac802154_beacon_worker(struct work_struct *work)
 	}
 
 	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(beacon_req->wpan_dev);
+	netdev_hold(sdata->dev, &dev_tracker, GFP_ATOMIC);
 
 	/* Wait an arbitrary amount of time in case we cannot use the device */
 	if (local->suspended || !ieee802154_sdata_running(sdata)) {
 		rcu_read_unlock();
 		queue_delayed_work(local->mac_wq, &local->beacon_work,
 				   msecs_to_jiffies(1000));
+		netdev_put(sdata->dev, &dev_tracker);
 		return;
 	}
 
@@ -450,6 +453,7 @@ void mac802154_beacon_worker(struct work_struct *work)
 	if (interval < IEEE802154_ACTIVE_SCAN_DURATION)
 		queue_delayed_work(local->mac_wq, &local->beacon_work,
 				   local->beacon_interval);
+	netdev_put(sdata->dev, &dev_tracker);
 }
 
 int mac802154_stop_beacons_locked(struct ieee802154_local *local,
-- 
2.43.0