ASoC: soc-compress.c: fix NULL dereference

commit d3268a40 upstream.

In soc_new_compress() when rtd->dai_link->dynamic is set, we create the pcm
substreams with this call:

   ret = snd_pcm_new_internal(rtd->card->snd_card, new_name, num,
                                   1, 0, &be_pcm);

which passes 0 as capture_count leading to

   be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream

being NULL, hence when trying to set rtd a few lines below we get an oops.

Fix by using rtd->dai_link->dpcm_playback and rtd->dai_link->dpcm_capture as
playback_count and capture_count to snd_pcm_new_internal().
Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

sound/soc/soc-compress.c

@@ -657,7 +657,8 @@ int soc_new_compress(struct snd_soc_pcm_runtime *rtd, int num)
 			rtd->dai_link->stream_name);
 
 		ret = snd_pcm_new_internal(rtd->card->snd_card, new_name, num,
-				1, 0, &be_pcm);
+				rtd->dai_link->dpcm_playback,
+				rtd->dai_link->dpcm_capture, &be_pcm);
 		if (ret < 0) {
 			dev_err(rtd->card->dev, "ASoC: can't create compressed for %s\n",
 				rtd->dai_link->name);
@@ -666,8 +667,10 @@ int soc_new_compress(struct snd_soc_pcm_runtime *rtd, int num)
 
 		rtd->pcm = be_pcm;
 		rtd->fe_compr = 1;
-		be_pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream->private_data = rtd;
-		be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream->private_data = rtd;
+		if (rtd->dai_link->dpcm_playback)
+			be_pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream->private_data = rtd;
+		else if (rtd->dai_link->dpcm_capture)
+			be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream->private_data = rtd;
 		memcpy(compr->ops, &soc_compr_dyn_ops, sizeof(soc_compr_dyn_ops));
 	} else
 		memcpy(compr->ops, &soc_compr_ops, sizeof(soc_compr_ops));