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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: syzbot+08a7d8b51ea048a74ffb@syzkaller.appspotmail.com
Fixes: a135dfb5de ("ALSA: led control - add sysfs kcontrol LED marking layer")
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210602034136.2762497-1-mudongliangabcd@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Dongliang Mu 2021-06-02 11:41:36 +08:00 committed by Takashi Iwai
parent 901be145a4
commit 3ae72f6ab9
1 changed files with 26 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
sound/core/control_led.c
View File

@ -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);
}