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References: <20211104062616.948353-1-albertccwang@google.com> <20211106012513.GA19852@jackp-linux.qualcomm.com>
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From:   Albert Wang <albertccwang@google.com>
Date:   Tue, 9 Nov 2021 13:10:13 +0800
Message-ID: <CANqn-rj3hJcKet=Fn3QwWqRZL11YfitBgjiE4kz-ttOfgqpARw@mail.gmail.com>
Subject: Re: [PATCH] usb: dwc3: gadget: Fix null pointer exception
To:     Jack Pham <quic_jackp@quicinc.com>
Cc:     balbi@kernel.org, gregkh@linuxfoundation.org, badhri@google.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Wesley Cheng <quic_wcheng@quicinc.com>
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Ok, let me do that.

Thanks,
Albert

On Sat, Nov 6, 2021 at 9:25 AM Jack Pham <quic_jackp@quicinc.com> wrote:
>
> On Thu, Nov 04, 2021 at 02:26:16PM +0800, Albert Wang wrote:
> > In the endpoint interrupt functions
> > dwc3_gadget_endpoint_transfer_in_progress() and
> > dwc3_gadget_endpoint_trbs_complete() will dereference the endpoint
> > descriptor. But it could be cleared in __dwc3_gadget_ep_disable()
> > when accessory disconnected. So we need to check whether it is null
> > or not before dereferencing it.
> >
> > Signed-off-by: Albert Wang <albertccwang@google.com>
>
> Nice catch.  I think this might have been caused when the call to
> dwc3_remove_requests() in __dwc3_gadget_ep_disable() was moved after
> the endpoint descriptors is cleared.  So you can probably add:
>
> Fixes: f09ddcfcb8c5 ("usb: dwc3: gadget: Prevent EP queuing while
> stopping transfers").
>
> Reviewed-by: Jack Pham <quic_jackp@quicinc.com>
>
> > ---
> >  drivers/usb/dwc3/gadget.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 23de2a5a40d6..83c7344888fd 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -3252,6 +3252,9 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
> >       struct dwc3             *dwc = dep->dwc;
> >       bool                    no_started_trb = true;
> >
> > +     if (!dep->endpoint.desc)
> > +             return no_started_trb;
> > +
> >       dwc3_gadget_ep_cleanup_completed_requests(dep, event, status);
> >
> >       if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
> > @@ -3299,6 +3302,9 @@ static void dwc3_gadget_endpoint_transfer_in_progress(struct dwc3_ep *dep,
> >  {
> >       int status = 0;
> >
> > +     if (!dep->endpoint.desc)
> > +             return;
> > +
> >       if (usb_endpoint_xfer_isoc(dep->endpoint.desc))
> >               dwc3_gadget_endpoint_frame_from_event(dep, event);
> >
> > --
> > 2.33.1.1089.g2158813163f-goog
> >