usb: hcd: Fix use after free in usb_hcd_pci_remove()

On the removal stage we put a reference to the controller structure and
if it's not used anymore it gets freed, but later we try to dereference
a pointer to a member of that structure.

Copy necessary field to a temporary variable to avoid use after free.

Fixes: 306c54d0 ("usb: hcd: Try MSI interrupts on PCI devices")
Reported-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/linux-usb/30a8c4ca-64c2-863b-cfcd-0970599c0ba3@huawei.com/Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200814182218.71957-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd-pci.c

@@ -315,11 +315,14 @@ EXPORT_SYMBOL_GPL(usb_hcd_pci_probe);
 void usb_hcd_pci_remove(struct pci_dev *dev)
 {
 	struct usb_hcd		*hcd;
+	int			hcd_driver_flags;
 
 	hcd = pci_get_drvdata(dev);
 	if (!hcd)
 		return;
 
+	hcd_driver_flags = hcd->driver->flags;
+
 	if (pci_dev_run_wake(dev))
 		pm_runtime_get_noresume(&dev->dev);
 
@@ -347,7 +350,7 @@ void usb_hcd_pci_remove(struct pci_dev *dev)
 		up_read(&companions_rwsem);
 	}
 	usb_put_hcd(hcd);
-	if ((hcd->driver->flags & HCD_MASK) < HCD_USB3)
+	if ((hcd_driver_flags & HCD_MASK) < HCD_USB3)
 		pci_free_irq_vectors(dev);
 	pci_disable_device(dev);
 }