[PATCH 5.10.y] drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback() - Linux-stable-mirror

18 Apr 2025

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
[Minor context change fixed]
Signed-off-by: Feng Liu Feng.Liu3@windriver.com
Signed-off-by: He Zhe Zhe.He@windriver.com
---
Verified the build test.
---
 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 9531ba54e95b..ba289572fca5 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme.c
@@ -826,7 +826,9 @@ void rtw_surveydone_event_callback(struct adapter	*adapter, u8 *pbuf)
    RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_surveydone_event_callback: fw_state:%x\n\n", get_fwstate(pmlmepriv)));
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);
    } else {
@@ -1753,11 +1755,11 @@ void rtw_scan_timeout_handler(struct timer_list *t)
DBG_871X(FUNC_ADPT_FMT" fw_state =%x\n", FUNC_ADPT_ARG(adapter), get_fwstate(pmlmepriv));
-	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);
 }
-- 
2.34.1



    