Code: static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
				 int op_flag,
				 unsigned int size,
				 unsigned int __user *tlv)
{
	struct user_element *ue = kcontrol->private_data;
	int change = 0;
	void *new_data;

	if (op_flag > 0) {
		if (size > 1024 * 128)	/* sane value */
			return -EINVAL;

 		new_data = memdup_user(tlv, size);
 		if (IS_ERR(new_data))
 			return PTR_ERR(new_data);
 		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;
 	} else {
		if (! ue->tlv_data_size || ! ue->tlv_data)
			return -ENXIO;
		if (size < ue->tlv_data_size)
			return -ENOSPC;
 		if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))
			return -EFAULT;
 	}
 	return change;
 }

Vulnerability Type: +Info 
CWE ID: CWE-362
Summary: Race condition in the tlv handler functionality in the snd_ctl_elem_user_tlv function in sound/core/control.c in the ALSA control implementation in the Linux kernel before 3.15.2 allows local users to obtain sensitive information from kernel memory by leveraging /dev/snd/controlCX access.
Commit Message: 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: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>