Re: [PATCH 6.2 regression fix] gpiolib: Fix using uninitialized lookup-flags on ACPI platforms

[Bartosz Golaszewski <brgl@bgdev.pl>]

On Thu, Dec 29, 2022 at 5:45 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Commit 8eb1f71e7acc ("gpiolib: consolidate GPIO lookups") refactors
> fwnode_get_named_gpiod() and gpiod_get_index() into a unified
> gpiod_find_and_request() helper.
>
> The old functions both initialized their local lookupflags variable to
> GPIO_LOOKUP_FLAGS_DEFAULT, but the new code leaves it uninitialized.
>
> This is a problem for at least ACPI platforms, where acpi_find_gpio()
> only does a bunch of *lookupflags |= GPIO_* statements and thus relies
> on the variable being initialized.
>
> The variable not being initialized leads to:
>
> 1. Potentially the wrong flags getting used
> 2. The check for conflicting lookup flags in gpiod_configure_flags():
>    "multiple pull-up, pull-down or pull-disable enabled, invalid config"
>    sometimes triggering, making the GPIO unavailable
>
> Restore the initialization of lookupflags to GPIO_LOOKUP_FLAGS_DEFAULT
> to fix this.
>
> Fixes: 8eb1f71e7acc ("gpiolib: consolidate GPIO lookups")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Note I'm not working and not reading work email until Monday January 9th.
> I hit this while doing some hobby stuff and I decided to send this out
> right away to avoid others potentially wasting time debugging this, but
> I will not see any replies until Monday January 9th.
> ---
>  drivers/gpio/gpiolib.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 5a66d9616d7c..939c776b9488 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -3905,8 +3905,8 @@ static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
>                                                 const char *label,
>                                                 bool platform_lookup_allowed)
>  {
> +       unsigned long lookupflags = GPIO_LOOKUP_FLAGS_DEFAULT;
>         struct gpio_desc *desc = ERR_PTR(-ENOENT);
> -       unsigned long lookupflags;
>         int ret;
>
>         if (!IS_ERR_OR_NULL(fwnode))
> --
> 2.38.1
>

Queued for fixes, thanks!

Bart