From 92bf4dd35801b4e3e73d3cc4beb5c929f75e0da6 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Sun, 18 Jun 2023 21:49:58 +0300 Subject: wifi: mac80211: agg-tx: prevent start/stop race 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 Signed-off-by: Gregory Greenman Link: https://lore.kernel.org/r/20230618214436.e5b52777462a.I0b2ed6658e81804279f5d7c9c1918cb1f6626bf2@changeid Signed-off-by: Johannes Berg --- net/mac80211/agg-tx.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'net/mac80211') 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 */ -- cgit