Re: [PATCH] USB: serial: suppress driver bind attributes

[Johan Hovold <johan@kernel.org>]

On Thu, Jan 16, 2020 at 05:18:29PM +0100, Greg Kroah-Hartman wrote:
> On Thu, Jan 16, 2020 at 05:07:05PM +0100, Johan Hovold wrote:
> > USB-serial drivers must not be unbound from their ports before the
> > corresponding USB driver is unbound from the parent interface so
> > suppress the bind and unbind attributes.
> > 
> > Unbinding a serial driver while it's port is open is a sure way to
> > trigger a crash as any driver state is released on unbind while port
> > hangup is handled on the parent USB interface level. Drivers for
> > multiport devices where ports share a resource such as an interrupt
> > endpoint also generally cannot handle individual ports going away.
> > 
> > Cc: stable <stable@vger.kernel.org>
> > Signed-off-by: Johan Hovold <johan@kernel.org>
> > ---
> >  drivers/usb/serial/usb-serial.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
> > index 8f066bb55d7d..dc7a65b9ec98 100644
> > --- a/drivers/usb/serial/usb-serial.c
> > +++ b/drivers/usb/serial/usb-serial.c
> > @@ -1317,6 +1317,9 @@ static int usb_serial_register(struct usb_serial_driver *driver)
> >  		return -EINVAL;
> >  	}
> >  
> > +	/* Prevent individual ports from being unbound. */
> > +	driver->driver.suppress_bind_attrs = true;
> 
> We can still unbind the usb driver though, right?  If so, this is fine
> with me.

Right, this is only about disabling individual ports, something which
essentially no subdriver can handle while a port is open (e.g. port-data
set to NULL while port is still open... boom).

Johan