snd_pcm_sframes_t snd_pcm_lib_writev(struct snd_pcm_substream *substream,
				     void __user **bufs,
				     snd_pcm_uframes_t frames)
{
	struct snd_pcm_runtime *runtime;
	int nonblock;
	int err;

	err = pcm_sanity_check(substream);
	if (err < 0)
		return err;
	runtime = substream->runtime;
	nonblock = !!(substream->f_flags & O_NONBLOCK);

	if (runtime->access != SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
		return -EINVAL;
	return snd_pcm_lib_write1(substream, (unsigned long)bufs, frames,
				  nonblock, snd_pcm_lib_writev_transfer);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.