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   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Sat, 26 Mar 2022 23:58:35 +0100
   3 Subject: [PATCH] mac80211: do not wake queues on a vif that is being stopped
   4
   5 When a vif is being removed and sdata->bss is cleared, __ieee80211_wake_txqs
   6 can still be called on it, which crashes as soon as sdata->bss is being
   7 dereferenced.
   8 To fix this properly, check for SDATA_STATE_RUNNING before waking queues,
   9 and take the fq lock when setting it (to ensure that __ieee80211_wake_txqs
  10 observes the change when running on a different CPU
  11
  12 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  13 ---
  14
  15 --- a/net/mac80211/iface.c
  16 +++ b/net/mac80211/iface.c
  17 @@ -377,7 +377,9 @@ static void ieee80211_do_stop(struct iee
  18         bool cancel_scan;
  19         struct cfg80211_nan_func *func;
  20
  21 +       spin_lock_bh(&local->fq.lock);
  22         clear_bit(SDATA_STATE_RUNNING, &sdata->state);
  23 +       spin_unlock_bh(&local->fq.lock);
  24
  25         cancel_scan = rcu_access_pointer(local->scan_sdata) == sdata;
  26         if (cancel_scan)
  27 --- a/net/mac80211/util.c
  28 +++ b/net/mac80211/util.c
  29 @@ -301,6 +301,9 @@ static void __ieee80211_wake_txqs(struct
  30         local_bh_disable();
  31         spin_lock(&fq->lock);
  32
  33 +       if (!test_bit(SDATA_STATE_RUNNING, &sdata->state))
  34 +               goto out;
  35 +
  36         if (sdata->vif.type == NL80211_IFTYPE_AP)
  37                 ps = &sdata->bss->ps;
  38