usb: gadget: pch_udc: Check if driver is present before calling ->setup()

Since we have a separate routine for VBUS sense, the interrupt may occur
before gadget driver is present. Hence, ->setup() call may oops the kernel:

[   55.245843] BUG: kernel NULL pointer dereference, address: 00000010
...
[   55.245843] EIP: pch_udc_isr.cold+0x162/0x33f
...
[   55.245843]  <IRQ>
[   55.245843]  ? pch_udc_svc_data_out+0x160/0x160

Check if driver is present before calling ->setup().

Fixes: f646cf94 ("USB device driver of Topcliff PCH")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210323153626.54908-2-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/pch_udc.c

@@ -2298,6 +2298,21 @@ static void pch_udc_svc_data_out(struct pch_udc_dev *dev, int ep_num)
 		pch_udc_set_dma(dev, DMA_DIR_RX);
 }
 
+static int pch_udc_gadget_setup(struct pch_udc_dev *dev)
+	__must_hold(&dev->lock)
+{
+	int rc;
+
+	/* In some cases we can get an interrupt before driver gets setup */
+	if (!dev->driver)
+		return -ESHUTDOWN;
+
+	spin_unlock(&dev->lock);
+	rc = dev->driver->setup(&dev->gadget, &dev->setup_data);
+	spin_lock(&dev->lock);
+	return rc;
+}
+
 /**
  * pch_udc_svc_control_in() - Handle Control IN endpoint interrupts
  * @dev:	Reference to the device structure
@@ -2369,15 +2384,12 @@ static void pch_udc_svc_control_out(struct pch_udc_dev *dev)
 			dev->gadget.ep0 = &dev->ep[UDC_EP0IN_IDX].ep;
 		else /* OUT */
 			dev->gadget.ep0 = &ep->ep;
-		spin_lock(&dev->lock);
 		/* If Mass storage Reset */
 		if ((dev->setup_data.bRequestType == 0x21) &&
 		    (dev->setup_data.bRequest == 0xFF))
 			dev->prot_stall = 0;
 		/* call gadget with setup data received */
-		setup_supported = dev->driver->setup(&dev->gadget,
-						     &dev->setup_data);
-		spin_unlock(&dev->lock);
+		setup_supported = pch_udc_gadget_setup(dev);
 
 		if (dev->setup_data.bRequestType & USB_DIR_IN) {
 			ep->td_data->status = (ep->td_data->status &
@@ -2625,9 +2637,7 @@ static void pch_udc_svc_intf_interrupt(struct pch_udc_dev *dev)
 		dev->ep[i].halted = 0;
 	}
 	dev->stall = 0;
-	spin_unlock(&dev->lock);
-	dev->driver->setup(&dev->gadget, &dev->setup_data);
-	spin_lock(&dev->lock);
+	pch_udc_gadget_setup(dev);
 }
 
 /**
@@ -2662,9 +2672,7 @@ static void pch_udc_svc_cfg_interrupt(struct pch_udc_dev *dev)
 	dev->stall = 0;
 
 	/* call gadget zero with setup data received */
-	spin_unlock(&dev->lock);
-	dev->driver->setup(&dev->gadget, &dev->setup_data);
-	spin_lock(&dev->lock);
+	pch_udc_gadget_setup(dev);
 }
 
 /**