usb: vhci-hcd: Do not drop references before new references are gained

commit afdcfd3 upstream.

At a few places the driver carries stale pointers
to references that can still be used. Make sure that does not happen.
This strictly speaking closes ZDI-CAN-22273, though there may be
similar races in the driver.

Signed-off-by: Oliver Neukum <[email protected]>
Cc: stable <[email protected]>
Acked-by: Shuah Khan <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/usb/usbip/vhci_hcd.c

@@ -745,6 +745,7 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 	 *
 	 */
 	if (usb_pipedevice(urb->pipe) == 0) {
+		struct usb_device *old;
 		__u8 type = usb_pipetype(urb->pipe);
 		struct usb_ctrlrequest *ctrlreq =
 			(struct usb_ctrlrequest *) urb->setup_packet;
@@ -755,14 +756,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 			goto no_need_xmit;
 		}
 
+		old = vdev->udev;
 		switch (ctrlreq->bRequest) {
 		case USB_REQ_SET_ADDRESS:
 			/* set_address may come when a device is reset */
 			dev_info(dev, "SetAddress Request (%d) to port %d\n",
 				 ctrlreq->wValue, vdev->rhport);
 
-			usb_put_dev(vdev->udev);
 			vdev->udev = usb_get_dev(urb->dev);
+			usb_put_dev(old);
 
 			spin_lock(&vdev->ud.lock);
 			vdev->ud.status = VDEV_ST_USED;
@@ -781,8 +783,8 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 				usbip_dbg_vhci_hc(
 					"Not yet?:Get_Descriptor to device 0 (get max pipe size)\n");
 
-			usb_put_dev(vdev->udev);
 			vdev->udev = usb_get_dev(urb->dev);
+			usb_put_dev(old);
 			goto out;
 
 		default:
@@ -1067,15 +1069,16 @@ static void vhci_shutdown_connection(struct usbip_device *ud)
 static void vhci_device_reset(struct usbip_device *ud)
 {
 	struct vhci_device *vdev = container_of(ud, struct vhci_device, ud);
+	struct usb_device *old = vdev->udev;
 	unsigned long flags;
 
 	spin_lock_irqsave(&ud->lock, flags);
 
 	vdev->speed  = 0;
 	vdev->devid  = 0;
 
-	usb_put_dev(vdev->udev);
 	vdev->udev = NULL;
+	usb_put_dev(old);
 
 	if (ud->tcp_socket) {
 		sockfd_put(ud->tcp_socket);