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>

1 files changed, 1 insertions, 5 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 286c7ee35e63..92bfedfd3fd2 100644
--- a/net/mac80211/util.c
+++ b/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);
-
-	list_for_each_entry(sdata, &local->interfaces, list)
-		if (ieee80211_sdata_running(sdata))
-			ieee80211_enable_keys(sdata);
+		ieee80211_reenable_keys(sdata);
 
 	/* Reconfigure sched scan if it was interrupted by FW restart */
 	mutex_lock(&local->mtx);