usb: dwc3: of-simple: fix use-after-free on remove

[Johan Hovold <johan@kernel.org>]

On Wed, Jun 13, 2018 at 12:39:18PM +0300, Felipe Balbi wrote:
> Roger Quadros <rogerq@ti.com> writes:

> > I'm still trying to get my head around this.
> >
> > in probe() we do
> > {
> > 	enable all clocks;
> >         pm_runtime_set_active(dev);
> >         pm_runtime_enable(dev);
> >         pm_runtime_get_sync(dev);
> > }
> >
> > How will runtime suspend work at all?
> > We're holding a positive RPM count in probe().
> 
> echo auto > /path/to/dwc3/power/control

That makes no difference, user space cannot modify the always-active
behaviour given that probe returns with a positive usage count.

> Granted, that get_sync() would've been better as a pm_runtime_forbid()

Yeah, that would allow user space some control, albeit in a way that
may override a user space configuration (as the platform device would
already have been registered).

Why are you trying to prevent runtime pm in the first place? Shouldn't
the device be allowed to suspend when it has no active child by default?

Johan
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