ASoC: SOF: topology: allocate string for tuples

The existing code point tuples[*num_copied_tuples].value.s to elem->string
which works fine if there is only one topology is handled and all the
tuples are handled before the topology fw is released. However, we will
handle multiple topologies and the tuples may be used after the topology
fw is release. Ues devm_kasprintf to allocate the string for the tuples
to avoid invalid access.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

Author: bardliao

sound/soc/sof/topology.c

@@ -571,7 +571,11 @@ static int sof_copy_tuples(struct snd_sof_dev *sdev, struct snd_soc_tplg_vendor_
 						continue;
 
 					tuples[*num_copied_tuples].token = tokens[j].token;
-					tuples[*num_copied_tuples].value.s = elem->string;
+					tuples[*num_copied_tuples].value.s =
+						devm_kasprintf(sdev->dev, GFP_KERNEL,
+							       "%s", elem->string);
+					if (!tuples[*num_copied_tuples].value.s)
+						return -ENOMEM;
 				} else {
 					struct snd_soc_tplg_vendor_value_elem *elem;