mac80211: fix scheduled scan rtnl deadlock

When changing cfg80211 to use RTNL locking, this caused a
deadlock in mac80211 as it calls cfg80211_sched_scan_stopped()
from a work item that's on a workqueue that is flushed with
the RTNL held.

Fix this by simply using schedule_work(), the work only needs
to finish running before the wiphy is unregistered, no other
synchronisation (e.g. with suspend) is really required since
for suspend userspace is already blocked anyway when we flush
the workqueue so will only pick up the event after resume.

Cc: stable@vger.kernel.org
Fixes: 5fe231e87372 ("cfg80211: vastly simplify locking")
Reported-and-tested-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 2 insertions, 1 deletions

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 21d5d44444d0..e765f77bb97a 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -1047,6 +1047,7 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)
 
         cancel_work_sync(&local->restart_work);
         cancel_work_sync(&local->reconfig_filter);
+        flush_work(&local->sched_scan_stopped_work);
 
         ieee80211_clear_tx_pending(local);
         rate_control_deinitialize(local);
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 5ad66a83ef7f..bcc4833d7542 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -1088,6 +1088,6 @@ void ieee80211_sched_scan_stopped(struct ieee80211_hw *hw)
 
         trace_api_sched_scan_stopped(local);
 
-        ieee80211_queue_work(&local->hw, &local->sched_scan_stopped_work);
+        schedule_work(&local->sched_scan_stopped_work);
 }
 EXPORT_SYMBOL(ieee80211_sched_scan_stopped);