Commit 3ae72f6a authored by Dongliang Mu's avatar Dongliang Mu Committed by Takashi Iwai
Browse files

ALSA: control led: fix memory leak in snd_ctl_led_register 



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: default avatar <syzbot+08a7d8b51ea048a74ffb@syzkaller.appspotmail.com>
Fixes: a135dfb5 ("ALSA: led control - add sysfs kcontrol LED marking layer")
Signed-off-by: default avatarDongliang Mu <mudongliangabcd@gmail.com>
Reviewed-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: default avatarJaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210602034136.2762497-1-mudongliangabcd@gmail.com


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 901be145

sound/core/control_led.c

+26 −7
Original line number Diff line number Diff line
@@ -17,6 +17,9 @@ MODULE_LICENSE("GPL"); 
#define MAX_LED (((SNDRV_CTL_ELEM_ACCESS_MIC_LED - SNDRV_CTL_ELEM_ACCESS_SPK_LED) \

			>> SNDRV_CTL_ELEM_ACCESS_LED_SHIFT) + 1)



#define to_led_card_dev(_dev) \

	container_of(_dev, struct snd_ctl_led_card, dev)



enum snd_ctl_led_mode {

	 MODE_FOLLOW_MUTE = 0,

	 MODE_FOLLOW_ROUTE,
@@ -371,6 +374,21 @@ static void snd_ctl_led_disconnect(struct snd_card *card) 
	snd_ctl_led_refresh();

}



static void snd_ctl_led_card_release(struct device *dev)

{

	struct snd_ctl_led_card *led_card = to_led_card_dev(dev);



	kfree(led_card);

}



static void snd_ctl_led_release(struct device *dev)

{

}



static void snd_ctl_led_dev_release(struct device *dev)

{

}



/*

 * sysfs

 */
@@ -663,6 +681,7 @@ static void snd_ctl_led_sysfs_add(struct snd_card *card) 
		led_card->number = card->number;

		led_card->led = led;

		device_initialize(&led_card->dev);

		led_card->dev.release = snd_ctl_led_card_release;

		if (dev_set_name(&led_card->dev, "card%d", card->number) < 0)

			goto cerr;

		led_card->dev.parent = &led->dev;
@@ -681,7 +700,6 @@ static void snd_ctl_led_sysfs_add(struct snd_card *card) 
		put_device(&led_card->dev);

cerr2:

		printk(KERN_ERR "snd_ctl_led: unable to add card%d", card->number);

		kfree(led_card);

	}

}
@@ -700,8 +718,7 @@ 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);

		kfree(led_card);

		device_unregister(&led_card->dev);

		led->cards[card->number] = NULL;

	}

}
@@ -723,6 +740,7 @@ static int __init snd_ctl_led_init(void) 


	device_initialize(&snd_ctl_led_dev);

	snd_ctl_led_dev.class = sound_class;

	snd_ctl_led_dev.release = snd_ctl_led_dev_release;

	dev_set_name(&snd_ctl_led_dev, "ctl-led");

	if (device_add(&snd_ctl_led_dev)) {

		put_device(&snd_ctl_led_dev);
@@ -733,15 +751,16 @@ static int __init snd_ctl_led_init(void) 
		INIT_LIST_HEAD(&led->controls);

		device_initialize(&led->dev);

		led->dev.parent = &snd_ctl_led_dev;

		led->dev.release = snd_ctl_led_release;

		led->dev.groups = snd_ctl_led_dev_attr_groups;

		dev_set_name(&led->dev, led->name);

		if (device_add(&led->dev)) {

			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 +786,9 @@ 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);

}