can: grcan: grcan_close(): fix deadlock

There are deadlocks caused by del_timer_sync(&priv->hang_timer) and
del_timer_sync(&priv->rr_timer) in grcan_close(), one of the deadlocks
are shown below:

   (Thread 1)              |      (Thread 2)
                           | grcan_reset_timer()
grcan_close()              |  mod_timer()
 spin_lock_irqsave() //(1) |  (wait a time)
 ...                       | grcan_initiate_running_reset()
 del_timer_sync()          |  spin_lock_irqsave() //(2)
 (wait timer to stop)      |  ...

We hold priv->lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler also need
priv->lock in position (2) of thread 2. As a result, grcan_close()
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.

Link: https://lore.kernel.org/all/20220425042400.66517-1-duoming@zju.edu.cn
Fixes: 6cec9b07fe6a ("can: grcan: Add device driver for GRCAN and GRHCAN cores")
Cc: stable@vger.kernel.org
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
index d0c5a7a60dafb9416109261bcfea9782223faef2..1189057b5d680cdb42b9de9ccf732831c0d651fd 100644 (file)
--- a/drivers/net/can/grcan.c
+++ b/drivers/net/can/grcan.c
@@ -1102,8 +1102,10 @@ static int grcan_close(struct net_device *dev)
 
        priv->closing = true;
        if (priv->need_txbug_workaround) {
+               spin_unlock_irqrestore(&priv->lock, flags);
                del_timer_sync(&priv->hang_timer);
                del_timer_sync(&priv->rr_timer);
+               spin_lock_irqsave(&priv->lock, flags);
        }
        netif_stop_queue(dev);
        grcan_stop_hardware(dev);