Commit 45daaa13 authored by Ilan Peer's avatar Ilan Peer Committed by Johannes Berg
Browse files

mac80211: Properly WARN on HW scan before restart 



The following race was possible:

1. The device driver requests HW restart.
2. A scan is requested from user space and is propagated
   to the driver. During this flow HW_SCANNING flag is set.
3. The thread that handles the HW restart is scheduled,
   and before starting the actual reconfiguration it
   checks that HW_SCANNING is not set. The flow does so
   without acquiring any lock, and thus the WARN fires.

Fix this by checking that HW_SCANNING is on only after RTNL is
acquired, i.e., user space scan request handling is no longer
in transit.

Signed-off-by: default avatarIlan Peer <ilan.peer@intel.com>
Signed-off-by: default avatarLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.8238ab3e19ab.I2693c581c70251472b4f9089e37e06fb2c18268f@changeid


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent dd3e4fc7

net/mac80211/main.c

+3 −4
Original line number Diff line number Diff line
@@ -257,14 +257,13 @@ static void ieee80211_restart_work(struct work_struct *work) 
	/* wait for scan work complete */

	flush_workqueue(local->workqueue);

	flush_work(&local->sched_scan_stopped_work);

	flush_work(&local->radar_detected_work);



	rtnl_lock();



	WARN(test_bit(SCAN_HW_SCANNING, &local->scanning),

	     "%s called with hardware scan in progress\n", __func__);



	flush_work(&local->radar_detected_work);

	/* we might do interface manipulations, so need both */

	rtnl_lock();

	wiphy_lock(local->hw.wiphy);

	list_for_each_entry(sdata, &local->interfaces, list) {

		/*

		 * XXX: there may be more work for other vif types and even