mwifiex: Fix possible ABBA deadlock

Quoting Jia-Ju Bai <baijiaju1990@gmail.com>:

  mwifiex_dequeue_tx_packet()
     spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 1432 (Lock A)
     mwifiex_send_addba()
       spin_lock_bh(&priv->sta_list_spinlock); --> Line 608 (Lock B)

  mwifiex_process_sta_tx_pause()
     spin_lock_bh(&priv->sta_list_spinlock); --> Line 398 (Lock B)
     mwifiex_update_ralist_tx_pause()
       spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 941 (Lock A)

Similar report for mwifiex_process_uap_tx_pause().

While the locking expectations in this driver are a bit unclear, the
Fixed commit only intended to protect the sta_ptr, so we can drop the
lock as soon as we're done with it.

IIUC, this deadlock cannot actually happen, because command event
processing (which calls mwifiex_process_sta_tx_pause()) is
sequentialized with TX packet processing (e.g.,
mwifiex_dequeue_tx_packet()) via the main loop (mwifiex_main_process()).
But it's good not to leave this potential issue lurking.

Fixes: f0f7c2275fb9 ("mwifiex: minor cleanups w/ sta_list_spinlock in cfg80211.c")
Cc: Douglas Anderson <dianders@chromium.org>
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Link: https://lore.kernel.org/linux-wireless/0e495b14-efbb-e0da-37bd-af6bd677ee2c@gmail.com/
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/YaV0pllJ5p/EuUat@google.com

diff --git a/drivers/net/wireless/marvell/mwifiex/sta_event.c b/drivers/net/wireless/marvell/mwifiex/sta_event.c
index 80e5d44..7d42c5d 100644 (file)
--- a/drivers/net/wireless/marvell/mwifiex/sta_event.c
+++ b/drivers/net/wireless/marvell/mwifiex/sta_event.c
@@ -365,10 +365,12 @@ static void mwifiex_process_uap_tx_pause(struct mwifiex_private *priv,
                sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac);
                if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) {
                        sta_ptr->tx_pause = tp->tx_pause;
+                       spin_unlock_bh(&priv->sta_list_spinlock);
                        mwifiex_update_ralist_tx_pause(priv, tp->peermac,
                                                       tp->tx_pause);
+               } else {
+                       spin_unlock_bh(&priv->sta_list_spinlock);
                }
-               spin_unlock_bh(&priv->sta_list_spinlock);
        }
 }
 
@@ -400,11 +402,13 @@ static void mwifiex_process_sta_tx_pause(struct mwifiex_private *priv,
                        sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac);
                        if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) {
                                sta_ptr->tx_pause = tp->tx_pause;
+                               spin_unlock_bh(&priv->sta_list_spinlock);
                                mwifiex_update_ralist_tx_pause(priv,
                                                               tp->peermac,
                                                               tp->tx_pause);
+                       } else {
+                               spin_unlock_bh(&priv->sta_list_spinlock);
                        }
-                       spin_unlock_bh(&priv->sta_list_spinlock);
                }
        }
 }