drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()

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>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme.c b/drivers/staging/rtl8723bs/core/rtw_mlme.c
index a45df775d535..f7db483a5641 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);
 }