can: kvaser_usb: Fix use of uninitialized completion

flush_comp is initialized when CMD_FLUSH_QUEUE is sent to the device and
completed when the device sends CMD_FLUSH_QUEUE_RESP.

This causes completion of uninitialized completion if the device sends
CMD_FLUSH_QUEUE_RESP before CMD_FLUSH_QUEUE is ever sent (e.g. as a
response to a flush by a previously bound driver, or a misbehaving
device).

Fix that by initializing flush_comp in kvaser_usb_init_one() like the
other completions.

This issue is only triggerable after RX URBs have been set up, i.e. the
interface has been opened at least once.

Cc: stable@vger.kernel.org
Fixes: aec5fb22 ("can: kvaser_usb: Add support for Kvaser USB hydra family")
Tested-by: Jimmy Assarsson <extja@kvaser.com>
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Link: https://lore.kernel.org/all/20221010150829.199676-3-extja@kvaser.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c

@@ -729,6 +729,7 @@ static int kvaser_usb_init_one(struct kvaser_usb *dev, int channel)
 	init_usb_anchor(&priv->tx_submitted);
 	init_completion(&priv->start_comp);
 	init_completion(&priv->stop_comp);
+	init_completion(&priv->flush_comp);
 	priv->can.ctrlmode_supported = 0;
 
 	priv->dev = dev;

drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c

@@ -1916,7 +1916,7 @@ static int kvaser_usb_hydra_flush_queue(struct kvaser_usb_net_priv *priv)
 {
 	int err;
 
-	init_completion(&priv->flush_comp);
+	reinit_completion(&priv->flush_comp);
 
 	err = kvaser_usb_hydra_send_simple_cmd(priv->dev, CMD_FLUSH_QUEUE,
 					       priv->channel);