git.openwrt.org Git - openwrt/staging/981213.git/blob

   1 From: Alexander Wetzel <alexander@wetzel-home.de>
   2 Date: Thu, 15 Sep 2022 14:41:20 +0200
   3 Subject: [PATCH] mac80211: Fix deadlock: Don't start TX while holding
   4  fq->lock
   5
   6 ieee80211_txq_purge() calls fq_tin_reset() and
   7 ieee80211_purge_tx_queue(); Both are then calling
   8 ieee80211_free_txskb(). Which can decide to TX the skb again.
   9
  10 There are at least two ways to get a deadlock:
  11
  12 1) When we have a TDLS teardown packet queued in either tin or frags
  13    ieee80211_tdls_td_tx_handle() will call ieee80211_subif_start_xmit()
  14    while we still hold fq->lock. ieee80211_txq_enqueue() will thus
  15    deadlock.
  16
  17 2) A variant of the above happens if aggregation is up and running:
  18    In that case ieee80211_iface_work() will deadlock with the original
  19    task: The original tasks already holds fq->lock and tries to get
  20    sta->lock after kicking off ieee80211_iface_work(). But the worker
  21    can get sta->lock prior to the original task and will then spin for
  22    fq->lock.
  23
  24 Avoid these deadlocks by not sending out any skbs when called via
  25 ieee80211_free_txskb().
  26
  27 Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
  28 ---
  29
  30 --- a/net/mac80211/status.c
  31 +++ b/net/mac80211/status.c
  32 @@ -698,7 +698,7 @@ static void ieee80211_report_used_skb(st
  33
  34                 if (!sdata) {
  35                         skb->dev = NULL;
  36 -               } else {
  37 +               } else if (!dropped) {
  38                         unsigned int hdr_size =
  39                                 ieee80211_hdrlen(hdr->frame_control);
  40