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

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

[Feng Liu]

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

Re: [PATCH 5.10.y] drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found follow-up fixes in mainline

The upstream commit SHA1 provided is correct: cc7ad0d77b51c872d629bcd98aea463a3c4109e7

WARNING: Author mismatch between patch and upstream commit:
Backport author: Feng Liu<Feng.Liu3@windriver.com>
Commit author: Duoming Zhou<duoming@zju.edu.cn>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (exact SHA1)
6.1.y | Present (exact SHA1)
5.15.y | Present (different SHA1: f89f6c3ebf69)

Found fixes commits:
3f467036093f drivers: staging: rtl8723bs: Fix locking in rtw_scan_timeout_handler()

Note: The patch differs from the upstream commit:
---
1:  cc7ad0d77b51c ! 1:  6fa69b9b220a6 drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()
    @@ Metadata
      ## Commit message ##
         drivers: staging: rtl8723bs: Fix deadlock in rtw_surveydone_event_callback()
     
    +    [ Upstream commit cc7ad0d77b51c872d629bcd98aea463a3c4109e7 ]
    +
         There is a deadlock in rtw_surveydone_event_callback(),
         which is shown below:
     
    @@ Commit message
         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>
     
      ## drivers/staging/rtl8723bs/core/rtw_mlme.c ##
     @@ drivers/staging/rtl8723bs/core/rtw_mlme.c: 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 {
      
     @@ drivers/staging/rtl8723bs/core/rtw_mlme.c: void rtw_scan_timeout_handler(struct timer_list *t)
    - 						  mlmepriv.scan_to_timer);
    - 	struct	mlme_priv *pmlmepriv = &adapter->mlmepriv;
    + 
    + 	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);
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Success    |  Success   |