[PATCH 4.5 091/124] mac80211: fix txq queue related crashes

[Greg Kroah-Hartman]

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michal Kazior <michal.kaz...@tieto.com>

commit 2a58d42c1e018ad514d4e23fd33fb2ded95d3ee6 upstream.

The driver can access the queue simultanously
while mac80211 tears down the interface. Without
spinlock protection this could lead to corrupting
sk_buff_head and subsequently to an invalid
pointer dereference.

Fixes: ba8c3d6f16a1 ("mac80211: add an intermediate software queue 
implementation")
Signed-off-by: Michal Kazior <michal.kaz...@tieto.com>
Signed-off-by: Johannes Berg <johannes.b...@intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 net/mac80211/iface.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -977,7 +977,10 @@ static void ieee80211_do_stop(struct iee
        if (sdata->vif.txq) {
                struct txq_info *txqi = to_txq_info(sdata->vif.txq);
 
+               spin_lock_bh(&txqi->queue.lock);
                ieee80211_purge_tx_queue(&local->hw, &txqi->queue);
+               spin_unlock_bh(&txqi->queue.lock);
+
                atomic_set(&sdata->txqs_len[txqi->txq.ac], 0);
        }