ASoC: qcom: q6apm-lpass-dais: Fix NULL pointer dereference if source graph failed

If earlier opening of source graph fails (e.g. ADSP rejects due to
incorrect audioreach topology), the graph is closed and
"dai_data->graph[dai->id]" is assigned NULL.  Preparing the DAI for sink
graph continues though and next call to q6apm_lpass_dai_prepare()
receives dai_data->graph[dai->id]=NULL leading to NULL pointer
exception:

  qcom-apm gprsvc:service:2:1: Error (1) Processing 0x01001002 cmd
  qcom-apm gprsvc:service:2:1: DSP returned error[1001002] 1
  q6apm-lpass-dais 30000000.remoteproc:glink-edge:gpr:service@1:bedais: fail to start APM port 78
  q6apm-lpass-dais 30000000.remoteproc:glink-edge:gpr:service@1:bedais: ASoC: error at snd_soc_pcm_dai_prepare on TX_CODEC_DMA_TX_3: -22
  Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a8
  ...
  Call trace:
   q6apm_graph_media_format_pcm+0x48/0x120 (P)
   q6apm_lpass_dai_prepare+0x110/0x1b4
   snd_soc_pcm_dai_prepare+0x74/0x108
   __soc_pcm_prepare+0x44/0x160
   dpcm_be_dai_prepare+0x124/0x1c0

Fixes: 30ad723 ("ASoC: qdsp6: audioreach: add q6apm lpass dai support")
Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>
Message-ID: <20250904101849.121503-2-krzysztof.kozlowski@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: krzk

sound/soc/qcom/qdsp6/q6apm-lpass-dais.c

@@ -213,8 +213,10 @@ static int q6apm_lpass_dai_prepare(struct snd_pcm_substream *substream, struct s
 
 	return 0;
 err:
-	q6apm_graph_close(dai_data->graph[dai->id]);
-	dai_data->graph[dai->id] = NULL;
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		q6apm_graph_close(dai_data->graph[dai->id]);
+		dai_data->graph[dai->id] = NULL;
+	}
 	return rc;
 }