[PATCH v2] usb: dwc3: avoid NULL access of usb_gadget_driver

From: Linyu Yuan
Date: Mon Jun 28 2021 - 21:51:44 EST


we found crash in dwc3_disconnect_gadget(),
it is because dwc->gadget_driver become NULL before async access.
7dc0c55e9f30 ('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.

Signed-off-by: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>
---

v2: add missing check in dwc3_reset_gadget(), found by Alan Stern.

drivers/usb/dwc3/core.h | 1 +
drivers/usb/dwc3/ep0.c | 10 ++++++----
drivers/usb/dwc3/gadget.c | 21 ++++++++++++++++-----
3 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index dccdf13b5f9e..5991766239ba 100644
--- a/drivers/usb/dwc3/core.h
+++ b/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;
};
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 3cd294264372..2f9e45eed228 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/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;
}

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index af6d7f157989..45f2bc0807e8 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/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);
--
2.25.1