On Mon, May 31, 2021 at 02:20:37PM +0800, Dongliang Mu wrote:
> On Mon, May 31, 2021 at 12:40 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> >
> > On Mon, May 31, 2021 at 11:03:36AM +0800, Dongliang Mu wrote:
> > > On Sat, May 29, 2021 at 5:35 AM 慕冬亮 <mudongliangabcd@xxxxxxxxx> wrote:
> > > >
> > > >
> > > >
> > > > > On May 28, 2021, at 10:05 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> > > > >
> > > > > On Fri, May 28, 2021 at 09:50:49PM +0800, Dongliang Mu wrote:
> > > > >>
> > > > >> Can you please give some advise on how to fix this WARN issue?
> > > > >
> > > > > But it feels like it spoils the fun if I write the commit... Anyway:
> > > >
> > > > It’s fine. I am still in the learning process. It’s also good to learn experience by comparing your patch and my patch.
> > > >
> > > > >
> > > > > regards,
> > > > > dan carpenter
> > > > >
> > > > > diff --git a/sound/core/control_led.c b/sound/core/control_led.c
> > > > > index 25f57c14f294..dd357abc1b58 100644
> > > > > --- a/sound/core/control_led.c
> > > > > +++ b/sound/core/control_led.c
> > > > > @@ -740,6 +740,7 @@ static int __init snd_ctl_led_init(void)
> > > > > for (; group > 0; group--) {
> > > > > led = &snd_ctl_leds[group - 1];
> > > > > device_del(&led->dev);
> > > > > + device_put(&led->dev);
> > > > > }
> > > > > device_del(&snd_ctl_led_dev);
> > > > > return -ENOMEM;
> > > > > @@ -768,6 +769,7 @@ static void __exit snd_ctl_led_exit(void)
> > > > > for (group = 0; group < MAX_LED; group++) {
> > > > > led = &snd_ctl_leds[group];
> > > > > device_del(&led->dev);
> > > > > + device_put(&led->dev);
> > > > > }
> > > > > device_del(&snd_ctl_led_dev);
> > > > > snd_ctl_led_clean(NULL);
> > >
> > > Hi Dan,
> > >
> > > I tried this patch, and it still triggers the memleak.
> >
> > Did your patch fix the leak? Because my patch should have been
> > equivalent except for it fixes an additional leak in the snd_ctl_led_init()
> > error path.
>
> The syzbot link is [1]. I have tested my patch in the syzbot dashboard
> and my local workspace.
>
> I think the reason why your patch did not work should be
> led_card(struct snd_ctl_led_card) is already freed before returning in
> snd_ctl_led_sysfs_remove, rather than led(struct snd_ctl_led). See the
> implementation of snd_ctl_led_sysfs_remove for some details. Please
> correct me if I make any mistakes.
>
> static void snd_ctl_led_sysfs_remove(struct snd_card *card)
> {
> unsigned int group;
> struct snd_ctl_led_card *led_card;
> struct snd_ctl_led *led;
> char link_name[32];
>
> for (group = 0; group < MAX_LED; group++) {
> led = &snd_ctl_leds[group];
> led_card = led->cards[card->number];
> if (!led_card)
> continue;
> snprintf(link_name, sizeof(link_name), "led-%s", led->name);
> sysfs_remove_link(&card->ctl_dev.kobj, link_name);
> sysfs_remove_link(&led_card->dev.kobj, "card");
> device_del(&led_card->dev);
> put_device(&led_card->dev);
> kfree(led_card);
> led->cards[card->number] = NULL;
> }
> }
This is frustrating to look at because it's not a diff so it doesn't
show what you changed. I think you are saying that you added the
put_device(&led_card->dev);. That's true. There are some other leaks
as well. We should just fix them all. Use device_unregister() because
it's cleaner.
If both device_initialize() and device_add() succeed then call
device_unregister() to unwind.
diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index 25f57c14f294..561fe45e4449 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -700,7 +700,7 @@ static void snd_ctl_led_sysfs_remove(struct snd_card *card)
snprintf(link_name, sizeof(link_name), "led-%s", led->name);
sysfs_remove_link(&card->ctl_dev.kobj, link_name);
sysfs_remove_link(&led_card->dev.kobj, "card");
- device_del(&led_card->dev);
+ device_unregister(&led_card->dev);
kfree(led_card);
led->cards[card->number] = NULL;
}
@@ -739,9 +739,9 @@ static int __init snd_ctl_led_init(void)
put_device(&led->dev);
for (; group > 0; group--) {
led = &snd_ctl_leds[group - 1];
- device_del(&led->dev);
+ device_unregister(&led->dev);
}
- device_del(&snd_ctl_led_dev);
+ device_unregister(&snd_ctl_led_dev);
return -ENOMEM;
}
}
@@ -767,9 +767,9 @@ static void __exit snd_ctl_led_exit(void)
}
for (group = 0; group < MAX_LED; group++) {
led = &snd_ctl_leds[group];
- device_del(&led->dev);
+ device_unregister(&led->dev);
}
- device_del(&snd_ctl_led_dev);
+ device_unregister(&snd_ctl_led_dev);
snd_ctl_led_clean(NULL);
}
