static int wait_for_avail(struct snd_pcm_substream *substream,
			      snd_pcm_uframes_t *availp)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	int is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
	wait_queue_t wait;
	int err = 0;
	snd_pcm_uframes_t avail = 0;
	long wait_time, tout;

	init_waitqueue_entry(&wait, current);
	set_current_state(TASK_INTERRUPTIBLE);
	add_wait_queue(&runtime->tsleep, &wait);

	if (runtime->no_period_wakeup)
		wait_time = MAX_SCHEDULE_TIMEOUT;
	else {
		wait_time = 10;
		if (runtime->rate) {
			long t = runtime->period_size * 2 / runtime->rate;
			wait_time = max(t, wait_time);
		}
		wait_time = msecs_to_jiffies(wait_time * 1000);
	}

	for (;;) {
		if (signal_pending(current)) {
			err = -ERESTARTSYS;
			break;
		}

		/*
		 * We need to check if space became available already
		 * (and thus the wakeup happened already) first to close
		 * the race of space already having become available.
		 * This check must happen after been added to the waitqueue
		 * and having current state be INTERRUPTIBLE.
		 */
		if (is_playback)
			avail = snd_pcm_playback_avail(runtime);
		else
			avail = snd_pcm_capture_avail(runtime);
		if (avail >= runtime->twake)
			break;
		snd_pcm_stream_unlock_irq(substream);

		tout = schedule_timeout(wait_time);

		snd_pcm_stream_lock_irq(substream);
		set_current_state(TASK_INTERRUPTIBLE);
		switch (runtime->status->state) {
		case SNDRV_PCM_STATE_SUSPENDED:
			err = -ESTRPIPE;
			goto _endloop;
		case SNDRV_PCM_STATE_XRUN:
			err = -EPIPE;
			goto _endloop;
		case SNDRV_PCM_STATE_DRAINING:
			if (is_playback)
				err = -EPIPE;
			else 
				avail = 0; /* indicate draining */
			goto _endloop;
		case SNDRV_PCM_STATE_OPEN:
		case SNDRV_PCM_STATE_SETUP:
		case SNDRV_PCM_STATE_DISCONNECTED:
			err = -EBADFD;
			goto _endloop;
		case SNDRV_PCM_STATE_PAUSED:
			continue;
		}
		if (!tout) {
			pcm_dbg(substream->pcm,
				"%s write error (DMA or IRQ trouble?)\n",
				is_playback ? "playback" : "capture");
			err = -EIO;
			break;
		}
	}
 _endloop:
	set_current_state(TASK_RUNNING);
	remove_wait_queue(&runtime->tsleep, &wait);
	*availp = avail;
	return err;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.