chain-dma: fix potential NULL dereference

It has been reported that upon resume certain userspace software
tries to use chain DMA without proper initialisation. Prevent DSP
exceptions by checking for such cases.

Link: #10955
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Author: lyakh

src/audio/chain_dma.c

@@ -79,6 +79,12 @@ static int chain_host_start(struct comp_dev *dev)
 	struct chain_dma_data *cd = comp_get_drvdata(dev);
 	int err;
 
+	if (!cd->chan_host || !cd->chan_host->dma) {
+		comp_err(dev, "incomplete initialization detected, aborting host %p",
+			 cd->chan_host);
+		return -ENODEV;
+	}
+
 	err = dma_start(cd->chan_host->dma->z_dev, cd->chan_host->index);
 	if (err < 0)
 		return err;