[PATCH 5.4 077/320] mwifiex: Fix possible ABBA deadlock

Greg Kroah-Hartman
2022-01-24T19:32:12Z

From: Brian Norris <briannorris@chromium.org>

[ Upstream commit 1b8bb8919ef81bfc8873d223b9361f1685f2106d ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/marvell/mwifiex/sta_event.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/sta_event.c b/drivers/net/wireless/marvell/mwifiex/sta_event.c
index 5fdffb114913d..fd12093863801 100644
--- a/drivers/net/wireless/marvell/mwifiex/sta_event.c
+++ b/drivers/net/wireless/marvell/mwifiex/sta_event.c
@@ -364,10 +364,12 @@ 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);
}
}

@@ -399,11 +401,13 @@ 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);
}
}
}
--
2.34.1