linux-kernel - Re: [PATCH] gpiolib: fix lookup table matching

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Message-ID: <b03f3d6f-cb29-4f14-878b-c3a060c0745d@samsung.com>
Date: Thu, 8 Jan 2026 11:31:13 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>, Linus
	Walleij <linusw@...nel.org>, Bartosz Golaszewski <brgl@...nel.org>, Konrad
	Dybcio <konradybcio@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH] gpiolib: fix lookup table matching

On 08.01.2026 11:23, Bartosz Golaszewski wrote:
> If on any iteration in gpiod_find(), gpio_desc_table_match() returns
> NULL (which is normal and expected), we never reinitialize desc back to
> ERR_PTR(-ENOENT) and if we don't find a match later on, we will return
> NULL causing a NULL-pointer dereference in users not expecting it. Don't
> initialize desc, but return ERR_PTR(-ENOENT) explicitly at the end of
> the function.
>
> Fixes: 9700b0fccf38 ("gpiolib: allow multiple lookup tables per consumer")
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Closes: https://lore.kernel.org/all/00107523-7737-4b92-a785-14ce4e93b8cb@samsung.com/
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
> ---
>   drivers/gpio/gpiolib.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index fc382f43f9fc..0a14085f3871 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -4602,8 +4602,8 @@ static struct gpio_desc *gpio_desc_table_match(struct device *dev, const char *c
>   static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
>   				    unsigned int idx, unsigned long *flags)
>   {
> -	struct gpio_desc *desc = ERR_PTR(-ENOENT);
>   	struct gpiod_lookup_table *table;
> +	struct gpio_desc *desc;
>   
>   	guard(mutex)(&gpio_lookup_lock);
>   
> @@ -4619,7 +4619,7 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
>   		return desc;
>   	}
>   
> -	return desc;
> +	return ERR_PTR(-ENOENT);
>   }
>   
>   static int platform_gpio_count(struct device *dev, const char *con_id)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland