Re: [PATCH] ASoC: qcom: q6apm-lpass-dais: Fix NULL pointer dereference if source graph failed

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 15/08/2025 17:56, Srinivas Kandagatla wrote:
> Thanks Krzysztof,
> On 8/15/25 12:39 PM, Krzysztof Kozlowski wrote:
>> If earlier opening of source graph fails (e.g. ADSP rejects due to
> 
> I think you are referring to the err patch in prepare.

True I am working on feature relying on that other patch, but the code
here is not really relevant to that other patch, I think.

> 
>> 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: 30ad723b93ad ("ASoC: qdsp6: audioreach: add q6apm lpass dai support")
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> ---
>>  sound/soc/qcom/qdsp6/q6apm-lpass-dais.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/sound/soc/qcom/qdsp6/q6apm-lpass-dais.c b/sound/soc/qcom/qdsp6/q6apm-lpass-dais.c
>> index f90628d9b90e..7520e6f024c3 100644
>> --- a/sound/soc/qcom/qdsp6/q6apm-lpass-dais.c
>> +++ b/sound/soc/qcom/qdsp6/q6apm-lpass-dais.c
>> @@ -191,6 +191,12 @@ static int q6apm_lpass_dai_prepare(struct snd_pcm_substream *substream, struct s
>>  			return rc;
>>  		}
>>  		dai_data->graph[graph_id] = graph;
>> +	} else if (!dai_data->graph[dai->id]) {
>> +		/*
>> +		 * Loading source graph failed before, so abort loading the sink
>> +		 * as well.
>> +		 */
>> +		return -EINVAL;
>>  	}
> I guess this is the capture graph that is triggering the error, normally
> we do not open/close the capture graph in prepare, we do
> stop/prepare/start for capture graphs and handle open close in
> startup/shutdown.
> 
> Can you try this change and see if it fixes the issue, as prepare could
> be called multiple times and your patch will not give chance for trying
> new parameters incase the failure was due to unsupported params.


Yes, this works.

Best regards,
Krzysztof