[PATCH v2] ALSA: control led: fix memory leak in snd_ctl_led_register

[Jaroslav Kysela]

On 02. 06. 21 5:41, 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.
> 
> Reported-by: syzbot+08a7d8b51ea048a74ffb at syzkaller.appspotmail.com
> Fixes: a135dfb5de1 ("ALSA: led control - add sysfs kcontrol LED marking layer")
> Signed-off-by: Dongliang Mu <mudongliangabcd at gmail.com>

Many thanks to you and Dan to cover this.

Revieved-by: Jaroslav Kysela <perex at perex.cz>

-- 
Jaroslav Kysela <perex at perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.