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

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

[David Yang]

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);
-	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

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

[Luiz Angelo Daros de Luca]

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
>

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

[David Yang]

On Fri, Jun 19, 2026 at 4:12 AM Luiz Angelo Daros de Luca
<luizluca@gmail.com> wrote:
> 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.

I've checked the buffer is long enough to hold the name string while
relatively small (only 64B), so it should be safe for the stack.

> You can alternatively solve the leak using devm_kasprintf() (my
> choice) or adding a kfree() before leaving the function.

devm_kasprintf() still makes the memory unused (later in the driver)
and unusable (since normally you won't unload the switch driver until
shutdown), IMO.

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

[Linus Walleij]

On Thu, Jun 18, 2026 at 4:02 PM David Yang <mmyangfl@gmail.com> wrote:

> 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>

Good catch!
Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

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

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 18 Jun 2026 22:01:55 +0800 you wrote:
> 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>
> 
> [...]

Here is the summary with links:
  - [net] net: dsa: realtek: fix memory leak in rtl8366rb_setup_led()
    https://git.kernel.org/netdev/net/c/056a5087d87e

You are awesome, thank you!
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