[PATCH AUTOSEL 5.17 05/60] drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()

Sasha Levin
2022-06-07T18:52:30Z

From: Duoming Zhou <duoming@zju.edu.cn>

[ Upstream commit cc7ad0d77b51c872d629bcd98aea463a3c4109e7 ]

There is a deadlock in rtw_surveydone_event_callback(),
which is shown below:

(Thread 1) | (Thread 2)
| _set_timer()
rtw_surveydone_event_callback()| mod_timer()
spin_lock_bh() //(1) | (wait a time)
... | rtw_scan_timeout_handler()
del_timer_sync() | spin_lock_bh() //(2)
(wait timer to stop) | ...

We hold pmlmepriv->lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler
also need pmlmepriv->lock in position (2) of thread 2.
As a result, rtw_surveydone_event_callback() will block forever.

This patch extracts del_timer_sync() from the protection of
spin_lock_bh(), which could let timer handler to obtain
the needed lock. What`s more, we change spin_lock_bh() in
rtw_scan_timeout_handler() to spin_lock_irq(). Otherwise,
spin_lock_bh() will also cause deadlock() in timer handler.

Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220409061836.60529-1-duoming@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/staging/rtl8723bs/core/rtw_mlme.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme.c b/drivers/staging/rtl8723bs/core/rtw_mlme.c
index 9202223ebc0c..a6e5f2332e12 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme.c
@@ -751,7 +751,9 @@ void rtw_surveydone_event_callback(struct adapter *adapter, u8 *pbuf)
}

if (check_fwstate(pmlmepriv, _FW_UNDER_SURVEY)) {
+ spin_unlock_bh(&pmlmepriv->lock);
del_timer_sync(&pmlmepriv->scan_to_timer);
+ spin_lock_bh(&pmlmepriv->lock);
_clr_fwstate_(pmlmepriv, _FW_UNDER_SURVEY);
}

@@ -1586,11 +1588,11 @@ void rtw_scan_timeout_handler(struct timer_list *t)
mlmepriv.scan_to_timer);
struct mlme_priv *pmlmepriv = &adapter->mlmepriv;

- spin_lock_bh(&pmlmepriv->lock);
+ spin_lock_irq(&pmlmepriv->lock);

_clr_fwstate_(pmlmepriv, _FW_UNDER_SURVEY);

- spin_unlock_bh(&pmlmepriv->lock);
+ spin_unlock_irq(&pmlmepriv->lock);

rtw_indicate_scan_done(adapter, true);
}
--
2.35.1