linux-kernel - Re: [PATCH v2] ALSA: control led: fix memory leak in snd_ctl_led

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Date:   Wed, 2 Jun 2021 09:35:43 +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 v2] ALSA: control led: fix memory leak in
 snd_ctl_led_register

On Wed, Jun 02, 2021 at 11:41:36AM +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. In addition, we also free some other similar memory
> leaks in snd_ctl_led_init/snd_ctl_led_exit.
> 
> Fix this by replacing device_del to device_unregister
> in snd_ctl_led_sysfs_remove/snd_ctl_led_init/snd_ctl_led_exit.
> 
> Note that, when CONFIG_DEBUG_KOBJECT_RELEASE is enabled, put_device will
> call kobject_release and delay the release of kobject, which will cause
> use-after-free when the memory backing the kobject is freed at once.

(Hopefully it's clear to everyone that this is in the original code and
fixed in your patch).

> 
> 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>
> ---

Looks perfect to me!

Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>

regards,
dan carpenter