can: ems_usb: ems_usb_read_bulk_callback(): fix URB memory leak

Fix similar memory leak as in commit 7352e1d ("can: gs_usb:
gs_usb_receive_bulk_callback(): fix URB memory leak").

In ems_usb_open(), the URBs for USB-in transfers are allocated, added to
the dev->rx_submitted anchor and submitted. In the complete callback
ems_usb_read_bulk_callback(), the URBs are processed and resubmitted. In
ems_usb_close() the URBs are freed by calling
usb_kill_anchored_urbs(&dev->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 ems_usb_close().

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

Fixes: 702171a ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260116-can_usb-fix-memory-leak-v2-1-4b8cb2915571@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: marckleinebudde

drivers/net/can/usb/ems_usb.c

@@ -486,11 +486,17 @@ static void ems_usb_read_bulk_callback(struct urb *urb)
 			  urb->transfer_buffer, RX_BUFFER_SIZE,
 			  ems_usb_read_bulk_callback, dev);
 
+	usb_anchor_urb(urb, &dev->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);
 }