Re: [PATCH 0/2] wifi: carl9170: revert broken devres conversions for input and hwrng

[Christian Lamparter <chunkeey@gmail.com>]

On 10/1/26 6:45 AM, Dmitry Torokhov wrote:
> Commits 23de0fa0d2a0 ("carl9170: devres-ing hwrng_register usage") and
> 87ddb2fc29f1 ("carl9170: devres-ing input_allocate_device") converted
> the HWRNG and WPS button input device registrations in carl9170 to
> devres attached to the parent struct usb_device (&ar->udev->dev) and
> removed the explicit unregistration calls from carl9170_unregister().
> 
> Because carl9170_register() runs asynchronously from the
> request_firmware_nowait() callback after probe has returned, and
> carl9170_usb_disconnect() frees struct ar9170 immediately in the
> interface disconnect callback before devres_release_all() runs, both the
> WPS input device (along with its ar->wps.name and ar->wps.phys strings)
> and the embedded struct hwrng remain registered after struct ar9170 has
> been freed, leading to use-after-free bugs.

? Do I have a different source there ?

carl9170_usb_disconnect() does a wait_for_completion(&ar->fw_load_wait)
before doing anything.

For this completion to be "completed" either the firmware loader callback
went as far as running through all the initialization (includes
carl9170_register(), which registers the WPS button + rng) successfully
and the device is up.

or if there was a grave error (usb protocol error, firmware not responding
the way we want) and the driver basically has to give up... (but then
carl9170_register would have never been able to even get as far as
registering the wps + rng)

Cheers,
Christian