From: Johannes Berg <johannes.berg@xxxxxxxxx>
There were crashes reported in this code, and the timer_shutdown()
warning in one of the previous patches indicates that the timeout
timer for the AP response (addba_resp_timer) is still armed while
we're stopping the aggregation session.
After a very long deliberation of the code, so far the only way I
could find that might cause this would be the following sequence:
- session start requested
- session start indicated to driver, but driver returns
IEEE80211_AMPDU_TX_START_DELAY_ADDBA
- session stop requested, sets HT_AGG_STATE_WANT_STOP
- session stop worker runs ___ieee80211_stop_tx_ba_session(),
sets HT_AGG_STATE_STOPPING
>From here on, the order doesn't matter exactly, but:
1. driver calls ieee80211_start_tx_ba_cb_irqsafe(),
setting HT_AGG_STATE_START_CB
2. driver calls ieee80211_stop_tx_ba_cb_irqsafe(),
setting HT_AGG_STATE_STOP_CB
3. the worker will run ieee80211_start_tx_ba_cb() for
HT_AGG_STATE_START_CB
4. the worker will run ieee80211_stop_tx_ba_cb() for
HT_AGG_STATE_STOP_CB
(the order could also be 1./3./2./4.)
This will cause ieee80211_start_tx_ba_cb() to send out the AddBA
request frame to the AP and arm the timer, but we're already in
the middle of stopping and so the ieee80211_stop_tx_ba_cb() will
no longer assume it needs to stop anything.
Prevent this by checking for WANT_STOP/STOPPING in the start CB,
and warn if we're sending a frame on a stopping session.
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Gregory Greenman <gregory.greenman@xxxxxxxxx>
---
net/mac80211/agg-tx.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index 118ad2e24dbb..b6b772685881 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -457,6 +457,10 @@ static void ieee80211_send_addba_with_timeout(struct sta_info *sta,
u8 tid = tid_tx->tid;
u16 buf_size;
+ if (WARN_ON_ONCE(test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state) ||
+ test_bit(HT_AGG_STATE_WANT_STOP, &tid_tx->state)))
+ return;
+
lockdep_assert_held(&sta->ampdu_mlme.mtx);
/* activate the timer for the recipient's addBA response */
@@ -802,6 +806,10 @@ void ieee80211_start_tx_ba_cb(struct sta_info *sta, int tid,
if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
return;
+ if (test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state) ||
+ test_bit(HT_AGG_STATE_WANT_STOP, &tid_tx->state))
+ return;
+
if (!test_bit(HT_AGG_STATE_SENT_ADDBA, &tid_tx->state)) {
ieee80211_send_addba_with_timeout(sta, tid_tx);
/* RESPONSE_RECEIVED state whould trigger the flow again */
--
2.38.1
