static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
					   unsigned long data,
					   snd_pcm_uframes_t size,
					   int nonblock,
					   transfer_f transfer)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	snd_pcm_uframes_t xfer = 0;
	snd_pcm_uframes_t offset = 0;
	snd_pcm_uframes_t avail;
	int err = 0;

	if (size == 0)
		return 0;

	snd_pcm_stream_lock_irq(substream);
	switch (runtime->status->state) {
	case SNDRV_PCM_STATE_PREPARED:
		if (size >= runtime->start_threshold) {
			err = snd_pcm_start(substream);
			if (err < 0)
				goto _end_unlock;
		}
		break;
	case SNDRV_PCM_STATE_DRAINING:
	case SNDRV_PCM_STATE_RUNNING:
	case SNDRV_PCM_STATE_PAUSED:
		break;
	case SNDRV_PCM_STATE_XRUN:
		err = -EPIPE;
		goto _end_unlock;
	case SNDRV_PCM_STATE_SUSPENDED:
		err = -ESTRPIPE;
		goto _end_unlock;
	default:
		err = -EBADFD;
		goto _end_unlock;
	}

	runtime->twake = runtime->control->avail_min ? : 1;
	if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)
		snd_pcm_update_hw_ptr(substream);
	avail = snd_pcm_capture_avail(runtime);
	while (size > 0) {
		snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
		snd_pcm_uframes_t cont;
		if (!avail) {
			if (runtime->status->state ==
			    SNDRV_PCM_STATE_DRAINING) {
				snd_pcm_stop(substream, SNDRV_PCM_STATE_SETUP);
				goto _end_unlock;
			}
			if (nonblock) {
				err = -EAGAIN;
				goto _end_unlock;
			}
			runtime->twake = min_t(snd_pcm_uframes_t, size,
					runtime->control->avail_min ? : 1);
			err = wait_for_avail(substream, &avail);
			if (err < 0)
				goto _end_unlock;
			if (!avail)
				continue; /* draining */
		}
		frames = size > avail ? avail : size;
		cont = runtime->buffer_size - runtime->control->appl_ptr % runtime->buffer_size;
		if (frames > cont)
			frames = cont;
		if (snd_BUG_ON(!frames)) {
			runtime->twake = 0;
			snd_pcm_stream_unlock_irq(substream);
			return -EINVAL;
		}
		appl_ptr = runtime->control->appl_ptr;
		appl_ofs = appl_ptr % runtime->buffer_size;
		snd_pcm_stream_unlock_irq(substream);
		err = transfer(substream, appl_ofs, data, offset, frames);
		snd_pcm_stream_lock_irq(substream);
		if (err < 0)
			goto _end_unlock;
		switch (runtime->status->state) {
		case SNDRV_PCM_STATE_XRUN:
			err = -EPIPE;
			goto _end_unlock;
		case SNDRV_PCM_STATE_SUSPENDED:
			err = -ESTRPIPE;
			goto _end_unlock;
		default:
			break;
		}
		appl_ptr += frames;
		if (appl_ptr >= runtime->boundary)
			appl_ptr -= runtime->boundary;
		runtime->control->appl_ptr = appl_ptr;
		if (substream->ops->ack)
			substream->ops->ack(substream);

		offset += frames;
		size -= frames;
		xfer += frames;
		avail -= frames;
	}
 _end_unlock:
	runtime->twake = 0;
	if (xfer > 0 && err >= 0)
		snd_pcm_update_state(substream, runtime);
	snd_pcm_stream_unlock_irq(substream);
	return xfer > 0 ? (snd_pcm_sframes_t)xfer : 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.