mac80211: clear crypto tx tailroom counter upon keys enable

In case we got a fw restart while roaming from encrypted AP to
non-encrypted one, we might end up with hitting a warning on the pending
counter crypto_tx_tailroom_pending_dec having a non-zero value.

The following comment taken from net/mac80211/key.c explains the rational
for the delayed tailroom needed:

	/*
	* The reason for the delayed tailroom needed decrementing is to
	* make roaming faster: during roaming, all keys are first deleted
	* and then new keys are installed. The first new key causes the
	* crypto_tx_tailroom_needed_cnt to go from 0 to 1, which invokes
	* the cost of synchronize_net() (which can be slow). Avoid this
	* by deferring the crypto_tx_tailroom_needed_cnt decrementing on
	* key removal for a while, so if we roam the value is larger than
	* zero and no 0->1 transition happens.
	*
	* The cost is that if the AP switching was from an AP with keys
	* to one without, we still allocate tailroom while it would no
	* longer be needed. However, in the typical (fast) roaming case
	* within an ESS this usually won't happen.
	*/

The next flow lead to the warning eventually reported as a bug:
1. Disconnect from encrypted AP
2. Set crypto_tx_tailroom_pending_dec = 1 for the key
3. Schedule work
4. Reconnect to non-encrypted AP
5. Add a new key, setting the tailroom counter = 1
6. Got FW restart while pending counter is set ---> hit the warning

While on it, the ieee80211_reset_crypto_tx_tailroom() func was merged into
its single caller ieee80211_reenable_keys (previously called
ieee80211_enable_keys). Also, we reset the crypto_tx_tailroom_pending_dec
and remove the counters warning as we just reset both.

Signed-off-by: Lior Cohen <lior2.cohen@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/20190830112451.21655-7-luca@coelho.fi
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/key.c

@@ -843,46 +843,30 @@ void ieee80211_key_free(struct ieee80211_key *key, bool delay_tailroom)
 	ieee80211_key_destroy(key, delay_tailroom);
 }
 
-void ieee80211_enable_keys(struct ieee80211_sub_if_data *sdata)
+void ieee80211_reenable_keys(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_key *key;
 	struct ieee80211_sub_if_data *vlan;
 
 	ASSERT_RTNL();
 
-	if (WARN_ON(!ieee80211_sdata_running(sdata)))
-		return;
-
-	mutex_lock(&sdata->local->key_mtx);
-
-	WARN_ON_ONCE(sdata->crypto_tx_tailroom_needed_cnt ||
-		     sdata->crypto_tx_tailroom_pending_dec);
-
-	if (sdata->vif.type == NL80211_IFTYPE_AP) {
-		list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
-			WARN_ON_ONCE(vlan->crypto_tx_tailroom_needed_cnt ||
-				     vlan->crypto_tx_tailroom_pending_dec);
-	}
-
-	list_for_each_entry(key, &sdata->key_list, list) {
-		increment_tailroom_need_count(sdata);
-		ieee80211_key_enable_hw_accel(key);
-	}
-
-	mutex_unlock(&sdata->local->key_mtx);
-}
-
-void ieee80211_reset_crypto_tx_tailroom(struct ieee80211_sub_if_data *sdata)
-{
-	struct ieee80211_sub_if_data *vlan;
-
 	mutex_lock(&sdata->local->key_mtx);
 
 	sdata->crypto_tx_tailroom_needed_cnt = 0;
+	sdata->crypto_tx_tailroom_pending_dec = 0;
 
 	if (sdata->vif.type == NL80211_IFTYPE_AP) {
-		list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
+		list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list) {
 			vlan->crypto_tx_tailroom_needed_cnt = 0;
+			vlan->crypto_tx_tailroom_pending_dec = 0;
+		}
+	}
+
+	if (ieee80211_sdata_running(sdata)) {
+		list_for_each_entry(key, &sdata->key_list, list) {
+			increment_tailroom_need_count(sdata);
+			ieee80211_key_enable_hw_accel(key);
+		}
 	}
 
 	mutex_unlock(&sdata->local->key_mtx);

net/mac80211/key.h

@@ -2,6 +2,7 @@
 /*
  * Copyright 2002-2004, Instant802 Networks, Inc.
  * Copyright 2005, Devicescape Software, Inc.
+ * Copyright (C) 2019 Intel Corporation
  */
 
 #ifndef IEEE80211_KEY_H
@@ -156,8 +157,7 @@ void ieee80211_free_keys(struct ieee80211_sub_if_data *sdata,
 			 bool force_synchronize);
 void ieee80211_free_sta_keys(struct ieee80211_local *local,
 			     struct sta_info *sta);
-void ieee80211_enable_keys(struct ieee80211_sub_if_data *sdata);
+void ieee80211_reenable_keys(struct ieee80211_sub_if_data *sdata);
-void ieee80211_reset_crypto_tx_tailroom(struct ieee80211_sub_if_data *sdata);
 
 #define key_mtx_dereference(local, ref) \
 	rcu_dereference_protected(ref, lockdep_is_held(&((local)->key_mtx)))

net/mac80211/util.c

@@ -2420,11 +2420,7 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 
 	/* add back keys */
 	list_for_each_entry(sdata, &local->interfaces, list)
-		ieee80211_reset_crypto_tx_tailroom(sdata);
+		ieee80211_reenable_keys(sdata);
-
-	list_for_each_entry(sdata, &local->interfaces, list)
-		if (ieee80211_sdata_running(sdata))
-			ieee80211_enable_keys(sdata);
 
 	/* Reconfigure sched scan if it was interrupted by FW restart */
 	mutex_lock(&local->mtx);