[PATCH] wifi: ipw2200: cancel qos_activate work on device removal

[HyunjungKo <hj351016@gmail.com>]

ipw_priv::qos_activate (handler ipw_bg_qos_activate) is scheduled on the
system workqueue from the QoS association/probe-response paths
(ipw_qos_association_resp(), ipw_handle_assoc_response()) via
schedule_work(&priv->qos_activate).

ipw_pci_remove() cancels ~two dozen other priv works with
cancel_work_sync()/cancel_delayed_work_sync() (associate, disassociate,
scan, rf_kill, roam, link_up/down, led_*, merge_networks, ...) but never
cancels qos_activate. The driver has no private workqueue, so the work
runs on the system workqueue and is not drained by any destroy_workqueue()
at teardown either.

If a qos_activate work is still pending when the device is removed,
ipw_pci_remove() goes on to free_irq(), free the libipw/netdev and
kfree(priv); the worker then dereferences the freed priv
(ipw_bg_qos_activate(): priv->mutex, priv->status, priv->assoc_network ->
ipw_qos_activate()) = use-after-free.

Cancel qos_activate alongside the other works in ipw_pci_remove(). The
handler takes priv->mutex and does not reschedule qos_activate, and this
cancel is not performed under priv->mutex, so cancel_work_sync() neither
deadlocks nor races a re-arm.

Found by code review; not reproduced. Trigger needs a QoS
association/probe-response frame racing device unbind. Same class as
commit (atm: fore200e) "fix use-after-free in tasklets during device
removal" and CVE-2024-27052 (wifi: rtl8xxxu): a teardown path that omits
cancelling an async callback racing the object free.

Signed-off-by: HyunjungKo <hj351016@gmail.com>
---
 drivers/net/wireless/intel/ipw2x00/ipw2200.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wireless/intel/ipw2x00/ipw2200.c b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
--- a/drivers/net/wireless/intel/ipw2x00/ipw2200.c
+++ b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
@@ -11786,5 +11786,6 @@ static void ipw_pci_remove(struct pci_dev *pdev)
 	cancel_delayed_work_sync(&priv->led_link_off);
 	cancel_delayed_work_sync(&priv->led_act_off);
 	cancel_work_sync(&priv->merge_networks);
+	cancel_work_sync(&priv->qos_activate);

 	/* Free MAC hash list for ADHOC */
--
2.43.0