Hi,
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> Felipe:
>
> On Thu, 29 Jun 2017, kernel test robot wrote:
>
>> FYI, we noticed the following commit:
>>
>> commit: f16443a034c7aa359ddf6f0f9bc40d01ca31faea ("USB: gadgetfs, dummy-hcd, net2280: fix locking for callbacks")
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>>
>> in testcase: trinity
>> with following parameters:
>>
>> runtime: 300s
>>
>> test-description: Trinity is a linux system call fuzz tester.
>> test-url: http://codemonkey.org.uk/projects/trinity/
>>
>>
>> on test machine: qemu-system-x86_64 -enable-kvm -m 420M
>>
>> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> ...
>
> I won't include the entire report. The gist is that we have a problem
> with lock ordering. The report is about dummy-hcd, but this could
> affect any UDC driver.
>
> 1. When a SETUP request arrives, composite_setup() acquires
> cdev->lock before calling the function driver's callback.
> When that callback submits a reply, it causes the UDC driver
> to acquire its private lock.
this only seems to happen before calling set_config():
case USB_REQ_SET_CONFIGURATION:
if (ctrl->bRequestType != 0)
goto unknown;
if (gadget_is_otg(gadget)) {
if (gadget->a_hnp_support)
DBG(cdev, "HNP available\n");
else if (gadget->a_alt_hnp_support)
DBG(cdev, "HNP on another port\n");
else
VDBG(cdev, "HNP inactive\n");
}
spin_lock(&cdev->lock);
value = set_config(cdev, ctrl, w_value);
spin_unlock(&cdev->lock);
break;
The "reply" here is a usb_ep_queue(gadget->ep0, req) call which should
hold UDC driver's private lock and disable interrupts for a short period
of time. Here's how it looks on dwc3:
int dwc3_gadget_ep0_queue(struct usb_ep *ep, struct usb_request *request,
gfp_t gfp_flags)
{
struct dwc3_request *req = to_dwc3_request(request);
struct dwc3_ep *dep = to_dwc3_ep(ep);
struct dwc3 *dwc = dep->dwc;
unsigned long flags;
int ret;
spin_lock_irqsave(&dwc->lock, flags);
if (!dep->endpoint.desc) {
dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
dep->name);
ret = -ESHUTDOWN;
goto out;
}
/* we share one TRB for ep0/1 */
if (!list_empty(&dep->pending_list)) {
ret = -EBUSY;
goto out;
}
ret = __dwc3_gadget_ep0_queue(dep, req);
out:
spin_unlock_irqrestore(&dwc->lock, flags);
return ret;
}
> 2. When a bus reset occurs, the UDC's interrupt handler acquires
> its private lock before calling usb_gadget_udc_reset(), which
> calls composite_disconnect(), which acquires cdev->lock.
The reset handler will only run after B has been released though, no?
Also, UDC should *release* its private lock before calling UDC reset:
static void dwc3_reset_gadget(struct dwc3 *dwc)
{
if (!dwc->gadget_driver)
return;
if (dwc->gadget.speed != USB_SPEED_UNKNOWN) {
spin_unlock(&dwc->lock);
usb_gadget_udc_reset(&dwc->gadget, dwc->gadget_driver);
spin_lock(&dwc->lock);
}
}
Are you sure this isn't a bug in dummy only?
--
balbi
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