Hi,
Magnus Lilja <lilja.magnus@xxxxxxxxx> writes:
>> Magnus Lilja <lilja.magnus@xxxxxxxxx> writes:
>>>>> I tried the fsl_udc_core gadget driver on the i.MX31 PDK board and got a
>>>>> kernel panic (NULL pointer dereference) when connecting the USB cable. I
>>>>> had the g_serial module loaded as well.
>>>>>
>>>>> The NULL pointer panic comes from gadget/udc/core.c
>>>>> usb_gadget_giveback_request() which calls req->complete() and in some
>>>>> cases req->complete is NULL.
>>>>>
>>>>> Commit 304f7e5e1d08 ("usb: gadget: Refactor request completion") changed
>>>>> fsl_udc2_core.c (and several other files) and in fsl_udc2_core.c a check
>>>>> that req->complete is non-NULL was removed:
>>>>>
>>>>> --- a/drivers/usb/gadget/udc/fsl_udc_core.c
>>>>> +++ b/drivers/usb/gadget/udc/fsl_udc_core.c
>>>>> @@ -197,10 +197,8 @@ __acquires(ep->udc->lock)
>>>>> ep->stopped = 1;
>>>>>
>>>>> spin_unlock(&ep->udc->lock);
>>>>> - /* complete() is from gadget layer,
>>>>> - * eg fsg->bulk_in_complete() */
>>>>> - if (req->req.complete)
>>>>> - req->req.complete(&ep->ep, &req->req);
>>>>> +
>>>>> + usb_gadget_giveback_request(&ep->ep, &req->req);
>>>>>
>>>>> spin_lock(&ep->udc->lock);
>>>>> ep->stopped = stopped;
>>>>>
>>>>> If I re-introduce the check (either in fsl_udc_core.c or core.c) at
>>>>> least USB gadget operation using g_serial seems to work just fine.
>>>>>
>>>>> I don't know the logic in detail to understand whether this is a proper
>>>>> fix or if there is some other more problem with the fls_udc_core driver.
>>>>> Does anyone have input in this matter?
>>>>>
>>>>> I can produce a proper patch that fixes this problem by re-introducing
>>>>> the check (in either fsl_udc_core.c or core.c) if that is a proper
>>>>> solution and I can also assist in testing other fixes to the problem.
>>>>
>>>> ->complete() is supposed to be mandatory. Which gadget do you have that
>>>> ->doesn't set ->complete() to a valid function pointer?
>>>
>>> I'm modprobing g_serial so the following modules are loaded (using my patch):
>>>
>>> ~ # lsmod
>>> usb_f_acm
>>> u_serial
>>> g_serial
>>> libcomposite
>>> configfs
>>> fsl_usb2_udc
>>
>> okay, can you figure out which request is coming without ->complete()
>> set? To which endpoint is this request being queued? It would be nice to
>> know these details. Maybe this is an old bug which ought to be fixed.
>
> Sure, I can try figure that out. Any input to make the debug of the
> faster is appreciated if you have any.
well, the easiest way is to add something like:
if (!req->complete)
dump_stack();
to fsl udc driver. Then you would know who queued the request without
->complete. A slightly better approach would be to:
if (WARN(!req->complete,
"%s: queueing request without ->complete\n", ep->name))
return;
Or something like that.
--
balbi
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