Re: [PATCH net] net: dsa: realtek: fix memory leak in rtl8366rb_setup_led()

[Luiz Angelo Daros de Luca <luizluca@gmail.com>]

Thanks David,


> led_classdev_register_ext() only reads init_data.devicename - it never
> stores the pointer. However, the caller allocated devicename with
> kasprintf() but never freed it, leaking the string memory.
>
> Fix it with a stack buffer to avoid dynamic buffers completely.
>
> Fixes: 32d617005475 ("net: dsa: realtek: add LED drivers for rtl8366rb")
> Signed-off-by: David Yang <mmyangfl@gmail.com>
> ---
>  drivers/net/dsa/realtek/rtl8366rb-leds.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/dsa/realtek/rtl8366rb-leds.c b/drivers/net/dsa/realtek/rtl8366rb-leds.c
> index 509ffd3f8db5..ba50d311cb15 100644
> --- a/drivers/net/dsa/realtek/rtl8366rb-leds.c
> +++ b/drivers/net/dsa/realtek/rtl8366rb-leds.c
> @@ -89,6 +89,7 @@ static int rtl8366rb_setup_led(struct realtek_priv *priv, struct dsa_port *dp,
>         struct led_init_data init_data = { };
>         enum led_default_state state;
>         struct rtl8366rb_led *led;
> +       char name[64];
>         u32 led_group;
>         int ret;
>
> @@ -129,10 +130,9 @@ static int rtl8366rb_setup_led(struct realtek_priv *priv, struct dsa_port *dp,
>         init_data.fwnode = led_fwnode;
>         init_data.devname_mandatory = true;
>
> -       init_data.devicename = kasprintf(GFP_KERNEL, "Realtek-%d:0%d:%d",
> -                                        dp->ds->index, dp->index, led_group);

Indeed, it will leak. init_data is local and init_data.devicename is
read by led_compose_name, not stored. However, stack is a limited
space for allocation.
You can alternatively solve the leak using devm_kasprintf() (my
choice) or adding a kfree() before leaving the function.

> -       if (!init_data.devicename)
> -               return -ENOMEM;
> +       snprintf(name, sizeof(name), "Realtek-%d:0%d:%d",
> +                dp->ds->index, dp->index, led_group);
> +       init_data.devicename = name;
>
>         ret = devm_led_classdev_register_ext(priv->dev, &led->cdev, &init_data);
>         if (ret) {
> --
> 2.53.0
>