void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	snd_pcm_uframes_t frames, ofs, transfer;

	if (runtime->silence_size < runtime->boundary) {
		snd_pcm_sframes_t noise_dist, n;
		if (runtime->silence_start != runtime->control->appl_ptr) {
			n = runtime->control->appl_ptr - runtime->silence_start;
			if (n < 0)
				n += runtime->boundary;
			if ((snd_pcm_uframes_t)n < runtime->silence_filled)
				runtime->silence_filled -= n;
			else
				runtime->silence_filled = 0;
			runtime->silence_start = runtime->control->appl_ptr;
		}
		if (runtime->silence_filled >= runtime->buffer_size)
			return;
		noise_dist = snd_pcm_playback_hw_avail(runtime) + runtime->silence_filled;
		if (noise_dist >= (snd_pcm_sframes_t) runtime->silence_threshold)
			return;
		frames = runtime->silence_threshold - noise_dist;
		if (frames > runtime->silence_size)
			frames = runtime->silence_size;
	} else {
		if (new_hw_ptr == ULONG_MAX) {	/* initialization */
			snd_pcm_sframes_t avail = snd_pcm_playback_hw_avail(runtime);
			if (avail > runtime->buffer_size)
				avail = runtime->buffer_size;
			runtime->silence_filled = avail > 0 ? avail : 0;
			runtime->silence_start = (runtime->status->hw_ptr +
						  runtime->silence_filled) %
						 runtime->boundary;
		} else {
			ofs = runtime->status->hw_ptr;
			frames = new_hw_ptr - ofs;
			if ((snd_pcm_sframes_t)frames < 0)
				frames += runtime->boundary;
			runtime->silence_filled -= frames;
			if ((snd_pcm_sframes_t)runtime->silence_filled < 0) {
				runtime->silence_filled = 0;
				runtime->silence_start = new_hw_ptr;
			} else {
				runtime->silence_start = ofs;
			}
		}
		frames = runtime->buffer_size - runtime->silence_filled;
	}
	if (snd_BUG_ON(frames > runtime->buffer_size))
		return;
	if (frames == 0)
		return;
	ofs = runtime->silence_start % runtime->buffer_size;
	while (frames > 0) {
		transfer = ofs + frames > runtime->buffer_size ? runtime->buffer_size - ofs : frames;
		if (runtime->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED ||
		    runtime->access == SNDRV_PCM_ACCESS_MMAP_INTERLEAVED) {
			if (substream->ops->silence) {
				int err;
				err = substream->ops->silence(substream, -1, ofs, transfer);
				snd_BUG_ON(err < 0);
			} else {
				char *hwbuf = runtime->dma_area + frames_to_bytes(runtime, ofs);
				snd_pcm_format_set_silence(runtime->format, hwbuf, transfer * runtime->channels);
			}
		} else {
			unsigned int c;
			unsigned int channels = runtime->channels;
			if (substream->ops->silence) {
				for (c = 0; c < channels; ++c) {
					int err;
					err = substream->ops->silence(substream, c, ofs, transfer);
					snd_BUG_ON(err < 0);
				}
			} else {
				size_t dma_csize = runtime->dma_bytes / channels;
				for (c = 0; c < channels; ++c) {
					char *hwbuf = runtime->dma_area + (c * dma_csize) + samples_to_bytes(runtime, ofs);
					snd_pcm_format_set_silence(runtime->format, hwbuf, transfer);
				}
			}
		}
		runtime->silence_filled += transfer;
		frames -= transfer;
		ofs = 0;
	}
}

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.