can: usb_8dev: usb_8dev_read_bulk_callback(): fix URB memory leak

Fix similar memory leak as in commit 7352e1d5932a ("can: gs_usb:
gs_usb_receive_bulk_callback(): fix URB memory leak").

In usb_8dev_open() -> usb_8dev_start(), the URBs for USB-in transfers are
allocated, added to the priv->rx_submitted anchor and submitted. In the
complete callback usb_8dev_read_bulk_callback(), the URBs are processed and
resubmitted. In usb_8dev_close() -> unlink_all_urbs() the URBs are freed by
calling usb_kill_anchored_urbs(&priv->rx_submitted).

However, this does not take into account that the USB framework unanchors
the URB before the complete function is called. This means that once an
in-URB has been completed, it is no longer anchored and is ultimately not
released in usb_kill_anchored_urbs().

Fix the memory leak by anchoring the URB in the
usb_8dev_read_bulk_callback() to the priv->rx_submitted anchor.

Fixes: 0024d8ad1639 ("can: usb_8dev: Add support for USB2CAN interface from 8 devices")
Cc: [e-mail]
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/usb/usb_8dev.c

···
 			  urb->transfer_buffer, RX_BUFFER_SIZE,
 			  usb_8dev_read_bulk_callback, priv);
 
+	usb_anchor_urb(urb, &priv->rx_submitted);
+
 	retval = usb_submit_urb(urb, GFP_ATOMIC);
+	if (!retval)
+		return;
+
+	usb_unanchor_urb(urb);
 
 	if (retval == -ENODEV)
 		netif_device_detach(netdev);
-	else if (retval)
+	else
 		netdev_err(netdev,
 			"failed resubmitting read bulk urb: %d\n", retval);
 }