Commit 6a66b01d authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: control: Don't embed ctl_dev 

Embedding the ctl_dev in the snd_card object may result in UAF when
the delayed kobj release is used; at the delayed kobj release, it
still accesses the struct device itself while the card memory (that
embeds the struct device) may be already gone.

As a workaround, detach the struct device from the card object by
allocating via the new snd_device_alloc() helper.  The rest are just
replacing ctl_dev access to the pointer.

This is based on the fix Curtis posted initially.  In this patch, the
changes are split and use the new helper function instead.

Link: https://lore.kernel.org/r/20230801171928.1460120-1-cujomalainey@chromium.org


Reviewed-by: default avatarJaroslav Kysela <perex@perex.cz>
Signed-off-by: default avatarCurtis Malainey <cujomalainey@chromium.org>
Tested-by: default avatarCurtis Malainey <cujomalainey@chromium.org>
Link: https://lore.kernel.org/r/20230816160252.23396-3-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 7f018db1

include/sound/core.h

+1 −1
Original line number Diff line number Diff line
@@ -96,7 +96,7 @@ struct snd_card { 
								private data */

	struct list_head devices;	/* devices */



	struct device ctl_dev;		/* control device */

	struct device *ctl_dev;		/* control device */

	unsigned int last_numid;	/* last used numeric ID */

	struct rw_semaphore controls_rwsem;	/* controls lock (list and values) */

	rwlock_t ctl_files_rwlock;	/* ctl_files list lock */

sound/core/control.c

+8 −6
Original line number Diff line number Diff line
@@ -2389,7 +2389,7 @@ static int snd_ctl_dev_register(struct snd_device *device) 
	int err;



	err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,

				  &snd_ctl_f_ops, card, &card->ctl_dev);

				  &snd_ctl_f_ops, card, card->ctl_dev);

	if (err < 0)

		return err;

	down_read(&card->controls_rwsem);
@@ -2425,7 +2425,7 @@ static int snd_ctl_dev_disconnect(struct snd_device *device) 
	up_read(&snd_ctl_layer_rwsem);

	up_read(&card->controls_rwsem);



	return snd_unregister_device(&card->ctl_dev);

	return snd_unregister_device(card->ctl_dev);

}



/*
@@ -2447,7 +2447,7 @@ static int snd_ctl_dev_free(struct snd_device *device) 
	xa_destroy(&card->ctl_hash);

#endif

	up_write(&card->controls_rwsem);

	put_device(&card->ctl_dev);

	put_device(card->ctl_dev);

	return 0;

}
@@ -2469,12 +2469,14 @@ int snd_ctl_create(struct snd_card *card) 
	if (snd_BUG_ON(card->number < 0 || card->number >= SNDRV_CARDS))

		return -ENXIO;



	snd_device_initialize(&card->ctl_dev, card);

	dev_set_name(&card->ctl_dev, "controlC%d", card->number);

	err = snd_device_alloc(&card->ctl_dev, card);

	if (err < 0)

		return err;

	dev_set_name(card->ctl_dev, "controlC%d", card->number);



	err = snd_device_new(card, SNDRV_DEV_CONTROL, card, &ops);

	if (err < 0)

		put_device(&card->ctl_dev);

		put_device(card->ctl_dev);

	return err;

}

sound/core/control_led.c

+2 −2
Original line number Diff line number Diff line
@@ -688,7 +688,7 @@ static void snd_ctl_led_sysfs_add(struct snd_card *card) 
			goto cerr;

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

		snprintf(link_name, sizeof(link_name), "led-%s", led->name);

		WARN(sysfs_create_link(&card->ctl_dev.kobj, &led_card->dev.kobj, link_name),

		WARN(sysfs_create_link(&card->ctl_dev->kobj, &led_card->dev.kobj, link_name),

			"can't create symlink to controlC%i device\n", card->number);

		WARN(sysfs_create_link(&led_card->dev.kobj, &card->card_dev.kobj, "card"),

			"can't create symlink to card%i\n", card->number);
@@ -714,7 +714,7 @@ static void snd_ctl_led_sysfs_remove(struct snd_card *card) 
		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(&card->ctl_dev->kobj, link_name);

		sysfs_remove_link(&led_card->dev.kobj, "card");

		device_unregister(&led_card->dev);

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

sound/usb/media.c

+1 −1
Original line number Diff line number Diff line
@@ -163,7 +163,7 @@ void snd_media_stop_pipeline(struct snd_usb_substream *subs) 


static int snd_media_mixer_init(struct snd_usb_audio *chip)

{

	struct device *ctl_dev = &chip->card->ctl_dev;

	struct device *ctl_dev = chip->card->ctl_dev;

	struct media_intf_devnode *ctl_intf;

	struct usb_mixer_interface *mixer;

	struct media_device *mdev = chip->media_dev;