Re: [PATCH v4 1/3] Bluetooth: Fix possible race with userspace of sysfs isoc_alt

Hsin-chen Chuang
2025-02-13T14:06:56Z

On Thu, Feb 13, 2025 at 9:45 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Thu, Feb 13, 2025 at 09:33:34PM +0800, Hsin-chen Chuang wrote:
> > On Thu, Feb 13, 2025 at 8:10 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > A: http://en.wikipedia.org/wiki/Top_post
> > > Q: Were do I find info about this thing called top-posting?
> > > A: Because it messes up the order in which people normally read text.
> > > Q: Why is top-posting such a bad thing?
> > > A: Top-posting.
> > > Q: What is the most annoying thing in e-mail?
> > >
> > > A: No.
> > > Q: Should I include quotations after my reply?
> > >
> > > http://daringfireball.net/2007/07/on_top
> > >
> > > On Thu, Feb 13, 2025 at 07:57:15PM +0800, Hsin-chen Chuang wrote:
> > > > The btusb driver data is allocated by devm_kzalloc and is
> > > > automatically freed on driver detach, so I guess we don't have
> > > > anything to do here.
> > >
> > > What? A struct device should NEVER be allocated with devm_kzalloc.
> > > That's just not going to work at all.
> >
> > Noted. Perhaps that needs to be refactored together.
> >
> > >
> > > > Or perhaps we should move btusb_disconnect's content here? Luiz, what
> > > > do you think?
> > >
> > > I think something is really wrong here. Why are you adding a new struct
> > > device to the system? What requires that? What is this new device
> > > going to be used for?
> >
> > The new device is only for exposing a new sysfs attribute.
>
> That feels crazy.
>
> > So originally we had a device called hci_dev, indicating the
> > implementation of the Bluetooth HCI layer. hci_dev is directly the
> > child of the usb_interface (the Bluetooth chip connected through USB).
> > Now I would like to add an attribute for something that's not defined
> > in the HCI layer, but lower layer only in Bluetooth USB.
> > Thus we want to rephrase the structure: usb_interface -> btusb (new
> > device) -> hci_dev, and then we could place the new attribute in the
> > new device.
> >
> > Basically I kept the memory management in btusb unchanged in this
> > patch, as the new device is only used for a new attribute.
> > Would you suggest we revise the memory management since we added a
> > device in this module?
>
> If you add a new device in the tree, it HAS to work properly with the
> driver core (i.e. life cycles are unique, you can't have empty release
> functions, etc.) Put it on the proper bus it belongs to, bind the
> needed drivers to it, and have it work that way, don't make a "fake"
> device for no good reason.

Got it. Thanks for the info.

Hi Luiz, I will work on v5 to make btusb resources managed by device.
Any concern?

>
> thanks,

>
> greg k-h

--
Best Regards,
Hsin-chen