lkml.org 
[lkml]   [2022]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 5.15 10/51] drivers: staging: rtl8192u: Fix deadlock in ieee80211_beacons_stop()
    Date
    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 1a193f900779..2b06706a7071 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)
    --
    2.35.1
    \
     
     \ /
      Last update: 2022-06-07 21:23    [W:4.100 / U:0.388 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site