[PATCH AUTOSEL 5.17 06/60] drivers: staging: rtl8192bs: Fix deadlock in rtw_joinbss_event_prehandle()

Sasha Levin
2022-06-07T19:06:44Z

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

[ Upstream commit 041879b12ddb0c6c83ed9c0bdd10dc82a056f2fc ]

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. What`s more, we change spin_lock_bh() to
spin_lock_irq() in _rtw_join_timeout_handler() in order to
prevent deadlock.

Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220409064953.67420-1-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 a6e5f2332e12..c29e3c68e61e 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));
}
@@ -1547,7 +1549,7 @@ void _rtw_join_timeout_handler(struct timer_list *t)
if (adapter->bDriverStopped || adapter->bSurpriseRemoved)
return;

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

if (rtw_to_roam(adapter) > 0) { /* join timeout caused by roaming */
while (1) {
@@ -1575,7 +1577,7 @@ void _rtw_join_timeout_handler(struct timer_list *t)

}

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

/*
--
2.35.1