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

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From: Oliver Neukum <oneukum@xxxxxxxx>

commit afdcfd3d6fcdeca2735ca8d994c5f2d24a368f0a 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 <oneukum@xxxxxxxx>
Cc: stable <stable@xxxxxxxxxx>
Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240709113851.14691-1-oneukum@xxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/usbip/vhci_hcd.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -751,6 +751,7 @@ static int vhci_urb_enqueue(struct usb_h
 	 *
 	 */
 	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;
@@ -761,14 +762,15 @@ static int vhci_urb_enqueue(struct usb_h
 			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;
@@ -787,8 +789,8 @@ static int vhci_urb_enqueue(struct usb_h
 				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:
@@ -1095,6 +1097,7 @@ static void vhci_shutdown_connection(str
 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);
@@ -1102,8 +1105,8 @@ static void vhci_device_reset(struct usb
 	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);


Patches currently in stable-queue which might be from oneukum@xxxxxxxx are

queue-4.19/usb-vhci-hcd-do-not-drop-references-before-new-references-are-gained.patch




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