[PATCH AUTOSEL 5.17 11/60] drivers: staging: rtl8192e: Fix deadlock in rtllib_beacons_stop()

Sasha Levin
2022-06-07T18:59:38Z

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

[ Upstream commit 9b6bdbd9337de3917945847bde262a34a87a6303 ]

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

(Thread 1) | (Thread 2)
| rtllib_send_beacon()
rtllib_beacons_stop() | mod_timer()
spin_lock_irqsave() //(1) | (wait a time)
... | rtllib_send_beacon_cb()
del_timer_sync() | spin_lock_irqsave() //(2)
(wait timer to stop) | ...

We hold ieee->beacon_lock in position (1) of thread 1 and
use del_timer_sync() to wait timer to stop, but timer handler
also need ieee->beacon_lock in position (2) of thread 2.
As a result, rtllib_beacons_stop() will block forever.

This patch extracts del_timer_sync() from the protection of
spin_lock_irqsave(), which could let timer handler to obtain
the needed lock.

Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220417141641.124388-1-duoming@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/staging/rtl8192e/rtllib_softmac.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8192e/rtllib_softmac.c b/drivers/staging/rtl8192e/rtllib_softmac.c
index 4b6c2295a3cf..b5a38f0a8d79 100644
--- a/drivers/staging/rtl8192e/rtllib_softmac.c
+++ b/drivers/staging/rtl8192e/rtllib_softmac.c
@@ -651,9 +651,9 @@ static void rtllib_beacons_stop(struct rtllib_device *ieee)
spin_lock_irqsave(&ieee->beacon_lock, flags);

ieee->beacon_txing = 0;
- del_timer_sync(&ieee->beacon_timer);

spin_unlock_irqrestore(&ieee->beacon_lock, flags);
+ del_timer_sync(&ieee->beacon_timer);

}

--
2.35.1