linux-kernel - Re: [PATCH v2 05/12] usb: otg-fsm: Fix hrtimer list corruption

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Message-ID: <20210705022151.GA12125@nchen>
Date:   Mon, 5 Jul 2021 10:21:51 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        David Heidelberg <david@...t.cz>, devicetree@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 05/12] usb: otg-fsm: Fix hrtimer list corruption

On 21-07-03 20:22:38, Dmitry Osipenko wrote:
> 03.07.2021 14:08, Peter Chen пишет:
> > On 21-07-02 02:43:10, Dmitry Osipenko wrote:
> >> The HNP work can be re-scheduled while it's still in-fly. This results in
> >> re-initialization of the busy work, resetting the hrtimer's list node of
> >> the work and crashing kernel with null dereference within kernel/timer
> >> once work's timer is expired. It's very easy to trigger this problem by
> >> re-plugging USB cable quickly. Initialize HNP work only once to fix this
> >> trouble.
> > 
> > Fully OTG compliance support has not maintained for years, what's the use case you
> > still want to use?
> 
> I don't have any use case for it, but I had CONFIG_USB_OTG_FSM=y and it
> was crashing kernel badly. The OTG works perfectly fine without the FSM.

You could add below at your dts to disable OTG FSM:
hnp-disable
srp-disable
adp-disable

Since there are no users for OTG FSM, it hasn't maintained for years,
I am not sure if it still works OK. If I remember correctly, the VBUS
will be off if you enable HNP, and the device at the host port will be
disconnected, that's may not your expectation.

-- 

Thanks,
Peter Chen