Re: [PATCH v3] gpiolib: fix reference leaks when removing GPIO chips still in use

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Fri, Aug 11, 2023 at 9:30 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
>
> After we remove a GPIO chip that still has some requested descriptors,
> gpiod_free_commit() will fail and we will never put the references to the
> GPIO device and the owning module in gpiod_free().
>
> Rework this function to:
> - not warn on desc == NULL as this is a use-case on which most free
>   functions silently return
> - put the references to desc->gdev and desc->gdev->owner unconditionally
>   so that the release callback actually gets called when the remaining
>   references are dropped by external GPIO users
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> ---
> v1 -> v2:
> - add a comment about why we can't use VALIDATE_DESC_VOID()
>
> v2 -> v3:
> - we must drop the reference to the owner module before we drop the one
>   to the gpio_device as the latter may be removed if this is the last
>   reference and we'll end up calling module_put() on freed memory

v3 looks good to me.
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij