Subject: [PATCH] mac80211: Ensure vif queues are operational after start
From: Alexander Wetzel <[email-masked]>
Date: Thu, 15 Sep 2022 15:09:46 +0200

Make sure local->queue_stop_reasons and vif.txqs_stopped stay in sync.

When a new vif is created the queues may end up in an inconsistent state
and be inoperable:
Communication not using iTXQ will work, allowing to e.g. complete the
association. But the 4-way handshake will time out. The sta will not
send out any skbs queued in iTXQs.

All normal attempts to start the queues will fail when reaching this
state.
local->queue_stop_reasons will have marked all queues as operational but
vif.txqs_stopped will still be set, creating an inconsistent internal
state.

In reality this seems to be race between the mac80211 function
ieee80211_do_open() setting SDATA_STATE_RUNNING and the wake_txqs_tasklet:
Depending on the driver and the timing the queues may end up to be
operational or not.

Cc: [email-masked]
Fixes: f856373e2f31 ("wifi: mac80211: do not wake queues on a vif that is being stopped")
Signed-off-by: Alexander Wetzel <[email-masked]>
---

--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -301,14 +301,14 @@ static void __ieee80211_wake_txqs(struct
 	local_bh_disable();
 	spin_lock(&fq->lock);
 
+	sdata->vif.txqs_stopped[ac] = false;
+
 	if (!test_bit(SDATA_STATE_RUNNING, &sdata->state))
 		goto out;
 
 	if (sdata->vif.type == NL80211_IFTYPE_AP)
 		ps = &sdata->bss->ps;
 
-	sdata->vif.txqs_stopped[ac] = false;
-
 	list_for_each_entry_rcu(sta, &local->sta_list, list) {
 		if (sdata != sta->sdata)
 			continue;