From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 806c7b53414934ba2a39449b31fd1a038e500273 ]
There is a deadlock in ieee80211_beacons_stop(), which is shown below:
(Thread 1) | (Thread 2) | ieee80211_send_beacon() ieee80211_beacons_stop() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | ieee80211_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, ieee80211_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/20220417135407.109536-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c index 1a43979939a8..79f3fbe25556 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c @@ -528,9 +528,9 @@ static void ieee80211_beacons_stop(struct ieee80211_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); }
void ieee80211_stop_send_beacons(struct ieee80211_device *ieee)