On 2021-06-26 00:37, Alan Stern wrote:
On Fri, Jun 25, 2021 at 06:44:15PM +0800, Linyu Yuan wrote:
there is following race condition,
CPU1 CPU2
dwc3_runtime_suspend() dwc3_gadget_stop()
spin_lock(&dwc->lock)
dwc3_gadget_suspend()
dwc3_disconnect_gadget()
dwc->gadget_driver != NULL
spin_unlock(&dwc->lock)
spin_lock(&dwc->lock)
dwc->gadget_driver = NULL
spin_unlock(&dwc->lock)
dwc->gadget_driver->disconnect(dwc->gadget);
system will crash when access NULL gadget_driver.
7dc0c55e9f30 ('USB: UDC core: Add udc_async_callbacks gadget op')
suggest a common way to avoid such kind of race.
this change implment the callback in dwc3 and
change related functions which have callback to UDC core.
Signed-off-by: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>
---
drivers/usb/dwc3/core.h | 1 +
drivers/usb/dwc3/ep0.c | 5 +++--
drivers/usb/dwc3/gadget.c | 39
+++++++++++++++++++++++----------------
3 files changed, 27 insertions(+), 18 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..26419077c7c9 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -597,10 +597,11 @@ 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 = 0;
spin_unlock(&dwc->lock);
- ret = dwc->gadget_driver->setup(dwc->gadget, ctrl);
+ if (dwc->async_callbacks)
+ ret = dwc->gadget_driver->setup(dwc->gadget, ctrl);
spin_lock(&dwc->lock);
Here and in the other places, you should test dwc->async_callbacks
_before_ dropping the spinlock. Otherwise there is a race (the flag
could be written at about the same time it is checked).
thanks for your comments,
if you think there is race here, how to make sure gadget_driver pointer
is safe,
this is closest place where we can confirm it is non-NULL by checking
async_callbacks ?
Alan Stern
return ret;
}
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index af6d7f157989..d868f30007cc 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,
};
/*
--------------------------------------------------------------------------
*/
@@ -3231,29 +3242,26 @@ static void dwc3_endpoint_interrupt(struct
dwc3 *dwc,
static void dwc3_disconnect_gadget(struct dwc3 *dwc)
{
- if (dwc->gadget_driver && dwc->gadget_driver->disconnect) {
- spin_unlock(&dwc->lock);
+ spin_unlock(&dwc->lock);
+ if (dwc->async_callbacks && dwc->gadget_driver->disconnect)
dwc->gadget_driver->disconnect(dwc->gadget);
- spin_lock(&dwc->lock);
- }
+ spin_lock(&dwc->lock);
}
static void dwc3_suspend_gadget(struct dwc3 *dwc)
{
- if (dwc->gadget_driver && dwc->gadget_driver->suspend) {
- spin_unlock(&dwc->lock);
+ spin_unlock(&dwc->lock);
+ if (dwc->async_callbacks && dwc->gadget_driver->suspend)
dwc->gadget_driver->suspend(dwc->gadget);
- spin_lock(&dwc->lock);
- }
+ spin_lock(&dwc->lock);
}
static void dwc3_resume_gadget(struct dwc3 *dwc)
{
- if (dwc->gadget_driver && dwc->gadget_driver->resume) {
- spin_unlock(&dwc->lock);
+ spin_unlock(&dwc->lock);
+ if (dwc->async_callbacks && dwc->gadget_driver->resume)
dwc->gadget_driver->resume(dwc->gadget);
- spin_lock(&dwc->lock);
- }
+ spin_lock(&dwc->lock);
}
static void dwc3_reset_gadget(struct dwc3 *dwc)
@@ -3585,11 +3593,10 @@ static void
dwc3_gadget_wakeup_interrupt(struct dwc3 *dwc)
* implemented.
*/
- if (dwc->gadget_driver && dwc->gadget_driver->resume) {
- spin_unlock(&dwc->lock);
+ spin_unlock(&dwc->lock);
+ if (dwc->async_callbacks && dwc->gadget_driver->resume)
dwc->gadget_driver->resume(dwc->gadget);
- spin_lock(&dwc->lock);
- }
+ spin_lock(&dwc->lock);
}
static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
--
2.25.1
