usb: dwc3: avoid NULL access of usb_gadget_driver

we found crash in dwc3_disconnect_gadget(),
it is because dwc->gadget_driver become NULL before async access.
7dc0c55 ('USB: UDC core: Add udc_async_callbacks gadget op')
suggest a common way to avoid such kind of issue.

this change implment the callback in dwc3 and
change related functions which have callback to usb gadget driver.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Linyu Yuan <linyyuan@codeaurora.org>
Link: https://lore.kernel.org/r/20210629015118.7944-1-linyyuan@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/core.h

@@ -1279,6 +1279,7 @@ struct dwc3 {
 	unsigned		dis_metastability_quirk:1;
 
 	unsigned		dis_split_quirk:1;
+	unsigned		async_callbacks:1;
 
 	u16			imod_interval;
 };

drivers/usb/dwc3/ep0.c

@@ -597,11 +597,13 @@ static int dwc3_ep0_set_address(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 
 static int dwc3_ep0_delegate_req(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 {
-	int ret;
+	int ret = -EINVAL;
 
-	spin_unlock(&dwc->lock);
-	ret = dwc->gadget_driver->setup(dwc->gadget, ctrl);
-	spin_lock(&dwc->lock);
+	if (dwc->async_callbacks) {
+		spin_unlock(&dwc->lock);
+		ret = dwc->gadget_driver->setup(dwc->gadget, ctrl);
+		spin_lock(&dwc->lock);
+	}
 	return ret;
 }
 

drivers/usb/dwc3/gadget.c

@@ -2585,6 +2585,16 @@ static int dwc3_gadget_vbus_draw(struct usb_gadget *g, unsigned int mA)
 	return ret;
 }
 
+static void dwc3_gadget_async_callbacks(struct usb_gadget *g, bool enable)
+{
+	struct dwc3		*dwc = gadget_to_dwc(g);
+	unsigned long		flags;
+
+	spin_lock_irqsave(&dwc->lock, flags);
+	dwc->async_callbacks = enable;
+	spin_unlock_irqrestore(&dwc->lock, flags);
+}
+
 static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.get_frame		= dwc3_gadget_get_frame,
 	.wakeup			= dwc3_gadget_wakeup,
@@ -2596,6 +2606,7 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.udc_set_ssp_rate	= dwc3_gadget_set_ssp_rate,
 	.get_config_params	= dwc3_gadget_config_params,
 	.vbus_draw		= dwc3_gadget_vbus_draw,
+	.udc_async_callbacks	= dwc3_gadget_async_callbacks,
 };
 
 /* -------------------------------------------------------------------------- */
@@ -3231,7 +3242,7 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
 
 static void dwc3_disconnect_gadget(struct dwc3 *dwc)
 {
-	if (dwc->gadget_driver && dwc->gadget_driver->disconnect) {
+	if (dwc->async_callbacks && dwc->gadget_driver->disconnect) {
 		spin_unlock(&dwc->lock);
 		dwc->gadget_driver->disconnect(dwc->gadget);
 		spin_lock(&dwc->lock);
@@ -3240,7 +3251,7 @@ static void dwc3_disconnect_gadget(struct dwc3 *dwc)
 
 static void dwc3_suspend_gadget(struct dwc3 *dwc)
 {
-	if (dwc->gadget_driver && dwc->gadget_driver->suspend) {
+	if (dwc->async_callbacks && dwc->gadget_driver->suspend) {
 		spin_unlock(&dwc->lock);
 		dwc->gadget_driver->suspend(dwc->gadget);
 		spin_lock(&dwc->lock);
@@ -3249,7 +3260,7 @@ static void dwc3_suspend_gadget(struct dwc3 *dwc)
 
 static void dwc3_resume_gadget(struct dwc3 *dwc)
 {
-	if (dwc->gadget_driver && dwc->gadget_driver->resume) {
+	if (dwc->async_callbacks && dwc->gadget_driver->resume) {
 		spin_unlock(&dwc->lock);
 		dwc->gadget_driver->resume(dwc->gadget);
 		spin_lock(&dwc->lock);
@@ -3261,7 +3272,7 @@ static void dwc3_reset_gadget(struct dwc3 *dwc)
 	if (!dwc->gadget_driver)
 		return;
 
-	if (dwc->gadget->speed != USB_SPEED_UNKNOWN) {
+	if (dwc->async_callbacks && dwc->gadget->speed != USB_SPEED_UNKNOWN) {
 		spin_unlock(&dwc->lock);
 		usb_gadget_udc_reset(dwc->gadget, dwc->gadget_driver);
 		spin_lock(&dwc->lock);
@@ -3585,7 +3596,7 @@ static void dwc3_gadget_wakeup_interrupt(struct dwc3 *dwc)
 	 * implemented.
 	 */
 
-	if (dwc->gadget_driver && dwc->gadget_driver->resume) {
+	if (dwc->async_callbacks && dwc->gadget_driver->resume) {
 		spin_unlock(&dwc->lock);
 		dwc->gadget_driver->resume(dwc->gadget);
 		spin_lock(&dwc->lock);