can: gs_usb: gs_can_open(): fix race dev->can.state condition

[ Upstream commit 5440428b3d ]

The dev->can.state is set to CAN_STATE_ERROR_ACTIVE, after the device
has been started. On busy networks the CAN controller might receive
CAN frame between and go into an error state before the dev->can.state
is assigned.

Assign dev->can.state before starting the controller to close the race
window.

Fixes: d08e973a77 ("can: gs_usb: Added support for the GS_USB CAN devices")
Link: https://lore.kernel.org/all/20220920195216.232481-1-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/can/usb/gs_usb.c

@@ -680,6 +680,7 @@ static int gs_can_open(struct net_device *netdev)
 		flags |= GS_CAN_MODE_TRIPLE_SAMPLE;
 
 	/* finally start device */
+	dev->can.state = CAN_STATE_ERROR_ACTIVE;
 	dm->mode = cpu_to_le32(GS_CAN_MODE_START);
 	dm->flags = cpu_to_le32(flags);
 	rc = usb_control_msg(interface_to_usbdev(dev->iface),
@@ -696,13 +697,12 @@ static int gs_can_open(struct net_device *netdev)
 	if (rc < 0) {
 		netdev_err(netdev, "Couldn't start device (err=%d)\n", rc);
 		kfree(dm);
+		dev->can.state = CAN_STATE_STOPPED;
 		return rc;
 	}
 
 	kfree(dm);
 
-	dev->can.state = CAN_STATE_ERROR_ACTIVE;
-
 	parent->active_channels++;
 	if (!(dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
 		netif_start_queue(netdev);