[PATCH 06/11] drivers: staging: rtl8192e: Fix deadlock in rtw_joinbss_event_prehandle()

[Duoming Zhou]

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

   (Thread 1)                |      (Thread 2)
                             | _set_timer()
rtw_joinbss_event_prehandle()|  mod_timer()
 spin_lock_bh() //(1)        |  (wait a time)
 ...                         | _rtw_join_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_joinbss_event_prehandle() 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.

Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
 drivers/staging/rtl8723bs/core/rtw_mlme.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme.c b/drivers/staging/rtl8723bs/core/rtw_mlme.c
index d559eefe633..5030556929d 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme.c
@@ -1240,8 +1240,10 @@ void rtw_joinbss_event_prehandle(struct adapter *adapter, u8 *pbuf)
 
 			spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
 
+			spin_unlock_bh(&pmlmepriv->lock);
 			/* s5. Cancel assoc_timer */
 			del_timer_sync(&pmlmepriv->assoc_timer);
+			spin_lock_bh(&pmlmepriv->lock);
 		} else {
 			spin_unlock_bh(&(pmlmepriv->scanned_queue.lock));
 		}
-- 
2.17.1