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From: Alexander Wetzel <alexander@wetzel-home.de>
Date: Thu, 15 Sep 2022 14:41:20 +0200
Subject: [PATCH] mac80211: Fix deadlock: Don't start TX while holding
fq->lock
ieee80211_txq_purge() calls fq_tin_reset() and
ieee80211_purge_tx_queue(); Both are then calling
ieee80211_free_txskb(). Which can decide to TX the skb again.
There are at least two ways to get a deadlock:
1) When we have a TDLS teardown packet queued in either tin or frags
ieee80211_tdls_td_tx_handle() will call ieee80211_subif_start_xmit()
while we still hold fq->lock. ieee80211_txq_enqueue() will thus
deadlock.
2) A variant of the above happens if aggregation is up and running:
In that case ieee80211_iface_work() will deadlock with the original
task: The original tasks already holds fq->lock and tries to get
sta->lock after kicking off ieee80211_iface_work(). But the worker
can get sta->lock prior to the original task and will then spin for
fq->lock.
Avoid these deadlocks by not sending out any skbs when called via
ieee80211_free_txskb().
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
---
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -698,7 +698,7 @@ static void ieee80211_report_used_skb(st
if (!sdata) {
skb->dev = NULL;
- } else {
+ } else if (!dropped) {
unsigned int hdr_size =
ieee80211_hdrlen(hdr->frame_control);
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