Patch "xhci: fix possible null pointer deref during xhci urb enqueue" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    xhci: fix possible null pointer deref during xhci urb enqueue

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xhci-fix-possible-null-pointer-deref-during-xhci-urb.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7cf220348e0433cc6254ec3b8f891f3fc2a941b5
Author: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Date:   Fri Dec 1 17:06:47 2023 +0200

    xhci: fix possible null pointer deref during xhci urb enqueue
    
    [ Upstream commit e2e2aacf042f52854c92775b7800ba668e0bdfe4 ]
    
    There is a short gap between urb being submitted and actually added to the
    endpoint queue (linked). If the device is disconnected during this time
    then usb core is not yet aware of the pending urb, and device may be freed
    just before xhci_urq_enqueue() continues, dereferencing the freed device.
    
    Freeing the device is protected by the xhci spinlock, so make sure we take
    and keep the lock while checking that device exists, dereference it, and
    add the urb to the queue.
    
    Remove the unnecessary URB check, usb core checks it before calling
    xhci_urb_enqueue()
    
    Suggested-by: Kuen-Han Tsai <khtsai@xxxxxxxxxx>
    Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231201150647.1307406-20-mathias.nyman@xxxxxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 132b76fa7ca60..e39c5ba9b7c76 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1498,24 +1498,7 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 	struct urb_priv	*urb_priv;
 	int num_tds;
 
-	if (!urb)
-		return -EINVAL;
-	ret = xhci_check_args(hcd, urb->dev, urb->ep,
-					true, true, __func__);
-	if (ret <= 0)
-		return ret ? ret : -EINVAL;
-
-	slot_id = urb->dev->slot_id;
 	ep_index = xhci_get_endpoint_index(&urb->ep->desc);
-	ep_state = &xhci->devs[slot_id]->eps[ep_index].ep_state;
-
-	if (!HCD_HW_ACCESSIBLE(hcd))
-		return -ESHUTDOWN;
-
-	if (xhci->devs[slot_id]->flags & VDEV_PORT_ERROR) {
-		xhci_dbg(xhci, "Can't queue urb, port error, link inactive\n");
-		return -ENODEV;
-	}
 
 	if (usb_endpoint_xfer_isoc(&urb->ep->desc))
 		num_tds = urb->number_of_packets;
@@ -1554,12 +1537,35 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 
 	spin_lock_irqsave(&xhci->lock, flags);
 
+	ret = xhci_check_args(hcd, urb->dev, urb->ep,
+			      true, true, __func__);
+	if (ret <= 0) {
+		ret = ret ? ret : -EINVAL;
+		goto free_priv;
+	}
+
+	slot_id = urb->dev->slot_id;
+
+	if (!HCD_HW_ACCESSIBLE(hcd)) {
+		ret = -ESHUTDOWN;
+		goto free_priv;
+	}
+
+	if (xhci->devs[slot_id]->flags & VDEV_PORT_ERROR) {
+		xhci_dbg(xhci, "Can't queue urb, port error, link inactive\n");
+		ret = -ENODEV;
+		goto free_priv;
+	}
+
 	if (xhci->xhc_state & XHCI_STATE_DYING) {
 		xhci_dbg(xhci, "Ep 0x%x: URB %p submitted for non-responsive xHCI host.\n",
 			 urb->ep->desc.bEndpointAddress, urb);
 		ret = -ESHUTDOWN;
 		goto free_priv;
 	}
+
+	ep_state = &xhci->devs[slot_id]->eps[ep_index].ep_state;
+
 	if (*ep_state & (EP_GETTING_STREAMS | EP_GETTING_NO_STREAMS)) {
 		xhci_warn(xhci, "WARN: Can't enqueue URB, ep in streams transition state %x\n",
 			  *ep_state);