ASoC: SOF: ipc3-control: Validate size in snd_sof_update_control

In snd_sof_update_control(), firmware-provided cdata->num_elems is
checked against local_cdata->data->size but never against the actual
allocation size. If local_cdata->data->size was previously set to an
inconsistent value, the memcpy could write past the allocated buffer.

Add a bounds check to ensure num_elems fits within the available space
in the ipc_control_data allocation before copying.

Fixes: 10f461d ("ASoC: SOF: Add IPC3 topology control ops")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

Author: ujfalusi

sound/soc/sof/ipc3-control.c

@@ -535,6 +535,15 @@ static void snd_sof_update_control(struct snd_sof_control *scontrol,
 			return;
 		}
 
+		/* Verify the size fits within the allocation */
+		if (cdata->num_elems > scontrol->max_size - sizeof(*local_cdata) -
+					sizeof(*local_cdata->data)) {
+			dev_err(scomp->dev,
+				"cdata binary size %u exceeds buffer\n",
+				cdata->num_elems);
+			return;
+		}
+
 		/* copy the new binary data */
 		memcpy(local_cdata->data, cdata->data, cdata->num_elems);
 	} else if (cdata->num_elems != scontrol->num_channels) {