Re: [PATCH] gpiolib: fix invalid pointer access in debugfs

[Ilya Gavrilov <ilyagv@gmail.com>]

Hi Bartosz,

On 10/31/25 18:06, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> If the memory allocation in gpiolib_seq_start() fails, the s->private
> field remains uninitialized and is later dereferenced without checking
> in gpiolib_seq_stop(). Initialize s->private to NULL before calling
> kzalloc() and check it before dereferencing it.
> 
> Fixes: e348544f7994 ("gpio: protect the list of GPIO devices with SRCU")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> ---
> This was brought to my attention by a person under sanctions. This is a
> simplified version of their initial patch.
> 
>  drivers/gpio/gpiolib.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index a81981336b36..fdb6a002dbda 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -5303,6 +5303,8 @@ static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
>  	struct gpio_device *gdev;
>  	loff_t index = *pos;
>  
> +	s->private = NULL;
> +
>  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
>  	if (!priv)
>  		return NULL;
> @@ -5338,6 +5340,9 @@ static void gpiolib_seq_stop(struct seq_file *s, void *v)
>  {
>  	struct gpiolib_seq_priv *priv = s->private;
>  
> +	if (!priv)
> +		return;
> +
>  	srcu_read_unlock(&gpio_devices_srcu, priv->idx);
>  	kfree(priv);
>  }

Maybe in this case it is better to signal an error and
explicitly return ERR_PTR(-ENOMEM) in gpiolib_seq_start(), rather than ignore it?