[PATCH] ASoC: fsl_asrc: check the second front-end DMA channel

The temporary Front-End DMA request can fail independently of the
persistent channel acquired earlier in fsl_asrc_dma_hw_params(). The
returned NULL pointer is immediately used to read its private data.

Check the temporary channel and release the previously acquired
persistent Front-End channel on failure. Clear its slot so a later
hw_free cannot release it twice. ASoC marks a component's hw_params
only after success and skips unmarked components during rollback, so
returning an error alone would leak the earlier channel.

Detected by static analysis and reviewed with AI-assisted source auditing.

Fixes: 3117bb3109dc ("ASoC: fsl_asrc: Add ASRC ASoC CPU DAI and platform drivers")
Assisted-by: LLM
Signed-off-by: Slavin Liu <redacted>
---
 sound/soc/fsl/fsl_asrc_dma.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
index 2f662bdf14d0..64f2b0612274 100644
--- a/sound/soc/fsl/fsl_asrc_dma.c
+++ b/sound/soc/fsl/fsl_asrc_dma.c

@@ -248,6 +248,11 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 
 		/* Get DMA request of Front-End */
 		tmp_chan = asrc->get_dma_channel(pair, dir);
+		if (!tmp_chan) {
+			dma_release_channel(pair->dma_chan[!dir]);
+			pair->dma_chan[!dir] = NULL;
+			return -EINVAL;
+		}
 		tmp_data = tmp_chan->private;
 		pair->dma_data.dma_request2 = tmp_data->dma_request;
 		pair->dma_data.peripheral_type = tmp_data->peripheral_type;