Commit 07f4d9d7 authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Takashi Iwai
Browse files

ALSA: control: Protect user controls against concurrent access 



The user-control put and get handlers as well as the tlv do not protect against
concurrent access from multiple threads. Since the state of the control is not
updated atomically it is possible that either two write operations or a write
and a read operation race against each other. Both can lead to arbitrary memory
disclosure. This patch introduces a new lock that protects user-controls from
concurrent access. Since applications typically access controls sequentially
than in parallel a single lock per card should be fine.

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Acked-by: default avatarJaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 7171511e

include/sound/core.h

+2 −0
Original line number Diff line number Diff line
@@ -116,6 +116,8 @@ struct snd_card { 
	int user_ctl_count;		/* count of all user controls */

	struct list_head controls;	/* all controls for this card */

	struct list_head ctl_files;	/* active control files */

	struct mutex user_ctl_lock;	/* protects user controls against

					   concurrent access */



	struct snd_info_entry *proc_root;	/* root for soundcard specific files */

	struct snd_info_entry *proc_id;	/* the card id */

sound/core/control.c

+25 −6
Original line number Diff line number Diff line
@@ -991,6 +991,7 @@ static int snd_ctl_elem_unlock(struct snd_ctl_file *file, 


struct user_element {

	struct snd_ctl_elem_info info;

	struct snd_card *card;

	void *elem_data;		/* element data */

	unsigned long elem_data_size;	/* size of element data in bytes */

	void *tlv_data;			/* TLV data */
@@ -1034,7 +1035,9 @@ static int snd_ctl_elem_user_get(struct snd_kcontrol *kcontrol, 
{

	struct user_element *ue = kcontrol->private_data;



	mutex_lock(&ue->card->user_ctl_lock);

	memcpy(&ucontrol->value, ue->elem_data, ue->elem_data_size);

	mutex_unlock(&ue->card->user_ctl_lock);

	return 0;

}
@@ -1044,9 +1047,11 @@ static int snd_ctl_elem_user_put(struct snd_kcontrol *kcontrol, 
	int change;

	struct user_element *ue = kcontrol->private_data;



	mutex_lock(&ue->card->user_ctl_lock);

	change = memcmp(&ucontrol->value, ue->elem_data, ue->elem_data_size) != 0;

	if (change)

		memcpy(ue->elem_data, &ucontrol->value, ue->elem_data_size);

	mutex_unlock(&ue->card->user_ctl_lock);

	return change;

}
@@ -1066,19 +1071,32 @@ static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol, 
		new_data = memdup_user(tlv, size);

		if (IS_ERR(new_data))

			return PTR_ERR(new_data);

		mutex_lock(&ue->card->user_ctl_lock);

		change = ue->tlv_data_size != size;

		if (!change)

			change = memcmp(ue->tlv_data, new_data, size);

		kfree(ue->tlv_data);

		ue->tlv_data = new_data;

		ue->tlv_data_size = size;

		mutex_unlock(&ue->card->user_ctl_lock);

	} else {

		if (! ue->tlv_data_size || ! ue->tlv_data)

			return -ENXIO;

		if (size < ue->tlv_data_size)

			return -ENOSPC;

		int ret = 0;



		mutex_lock(&ue->card->user_ctl_lock);

		if (!ue->tlv_data_size || !ue->tlv_data) {

			ret = -ENXIO;

			goto err_unlock;

		}

		if (size < ue->tlv_data_size) {

			ret = -ENOSPC;

			goto err_unlock;

		}

		if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))

			return -EFAULT;

			ret = -EFAULT;

err_unlock:

		mutex_unlock(&ue->card->user_ctl_lock);

		if (ret)

			return ret;

	}

	return change;

}
@@ -1210,6 +1228,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, 
	ue = kzalloc(sizeof(struct user_element) + private_size, GFP_KERNEL);

	if (ue == NULL)

		return -ENOMEM;

	ue->card = card;

	ue->info = *info;

	ue->info.access = 0;

	ue->elem_data = (char *)ue + sizeof(*ue);

sound/core/init.c

+1 −0
Original line number Diff line number Diff line
@@ -232,6 +232,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
	INIT_LIST_HEAD(&card->devices);

	init_rwsem(&card->controls_rwsem);

	rwlock_init(&card->ctl_files_rwlock);

	mutex_init(&card->user_ctl_lock);

	INIT_LIST_HEAD(&card->controls);

	INIT_LIST_HEAD(&card->ctl_files);

	spin_lock_init(&card->files_lock);

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