Messages in this thread | | | From | Dongliang Mu <> | Date | Fri, 28 May 2021 21:50:49 +0800 | Subject | Re: [PATCH] ALSA: control led: fix memory leak in snd_ctl_led_register |
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On Fri, May 28, 2021 at 9:33 PM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > 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@syzkaller.appspotmail.com > > Fixes: a135dfb5de1 ("ALSA: led control - add sysfs kcontrol LED marking layer") > > Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.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.
I see your point. This function I added is not to fix the root cause, but to fix an issue caused by the release function when the device is released.
The put_device is to fix the root cause(i.e., decrease the refcount to zero), however, the result is dev->p and kobject can be freed, but it will trigger a WARN [1] as it has no release method.
I don't know how to craft a release method for such a device. So this dummy function is generated following the default_release, also a dummy function.
Can you please give some advise on how to fix this WARN issue?
[1] https://elixir.bootlin.com/linux/latest/source/drivers/base/core.c#L2110
> > regards, > dan carpenter >
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