linux-kernel - Re: [PATCH] ALSA: control led: fix memory leak in snd_ctl_led

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Date:   Fri, 28 May 2021 16:33:09 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>
Cc:     perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
Subject: Re: [PATCH] ALSA: control led: fix memory leak in
 snd_ctl_led_register

On Fri, May 28, 2021 at 09:17:57PM +0800, Dongliang Mu wrote:
> The snd_ctl_led_sysfs_add and snd_ctl_led_sysfs_remove should contain
> the refcount operations in pair. However, snd_ctl_led_sysfs_remove fails
> to decrease the refcount to zero, which causes device_release never to
> be invoked. This leads to memory leak to some resources, like struct
> device_private.
> 
> Fix this by calling put_device at the end of snd_ctl_led_sysfs_remove
> 
> Reported-by: syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
> Fixes: a135dfb5de1 ("ALSA: led control - add sysfs kcontrol LED marking layer")
> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> ---
>  sound/core/control_led.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/sound/core/control_led.c b/sound/core/control_led.c
> index 25f57c14f294..fff2688b5019 100644
> --- a/sound/core/control_led.c
> +++ b/sound/core/control_led.c
> @@ -371,6 +371,10 @@ static void snd_ctl_led_disconnect(struct snd_card *card)
>  	snd_ctl_led_refresh();
>  }
>  
> +static void snd_ctl_led_release(struct device *dev)
> +{
> +}

Whatever you're trying to do, adding a dummy function is never the
answer.

regards,
dan carpenter