ASoC: SOF: ipc4-loader: Verify ext manifest magic number

Firmware image must start with an extended manifest. Add a check to make
sure that the image does contain it.

The magic number (the first u32 of a firmware image if manifest is present)
for an IPC4 image must be 0x31454124 (ASCI "$AE1").
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220823124219.927-1-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-loader.c

@@ -40,6 +40,17 @@ static size_t sof_ipc4_fw_parse_ext_man(struct snd_sof_dev *sdev)
 
 	ext_man_hdr = (struct sof_ext_manifest4_hdr *)fw->data;
 
+	/*
+	 * At the start of the firmware image we must have an extended manifest.
+	 * Verify that the magic number is correct.
+	 */
+	if (ext_man_hdr->id != SOF_EXT_MAN4_MAGIC_NUMBER) {
+		dev_err(sdev->dev,
+			"Unexpected extended manifest magic number: %#x\n",
+			ext_man_hdr->id);
+		return -EINVAL;
+	}
+
 	fw_hdr_offset = ipc4_data->manifest_fw_hdr_offset;
 	if (!fw_hdr_offset)
 		return -EINVAL;