[PATCH AUTOSEL 5.13 164/189] mac80211: Properly WARN on HW scan before restart

From: Sasha Levin
Date: Tue Jul 06 2021 - 07:28:06 EST

From: Ilan Peer <ilan.peer@xxxxxxxxx>

[ Upstream commit 45daaa1318410794de956fb8e9d06aed2dbb23d0 ]

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: Ilan Peer <ilan.peer@xxxxxxxxx>
Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.8238ab3e19ab.I2693c581c70251472b4f9089e37e06fb2c18268f@changeid
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
net/mac80211/main.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index f33a3acd7f96..2481bfdfafd0 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -257,14 +257,13 @@ static void ieee80211_restart_work(struct work_struct *work)
/* wait for scan work complete */
+ 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