linux-kernel - [PATCH] ALSA: control led: fix memory leak in snd_ctl_led

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Date:   Fri, 28 May 2021 21:17:57 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     perex@...ex.cz, tiwai@...e.com, dan.carpenter@...cle.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Cc:     Dongliang Mu <mudongliangabcd@...il.com>,
        syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
Subject: [PATCH] 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.

Fix this by calling put_device at the end of snd_ctl_led_sysfs_remove

Reported-by: syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
Fixes: a135dfb5de1 ("ALSA: led control - add sysfs kcontrol LED marking layer")
Signed-off-by: Dongliang Mu <mudongliangabcd@...il.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)
+{
+}
+
 /*
  * sysfs
  */
@@ -663,6 +667,7 @@ 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_release;
 		if (dev_set_name(&led_card->dev, "card%d", card->number) < 0)
 			goto cerr;
 		led_card->dev.parent = &led->dev;
@@ -701,6 +706,7 @@ static void snd_ctl_led_sysfs_remove(struct snd_card *card)
 		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;
 	}
-- 
2.25.1