ASoC: Intel: sst: Fix firmware name size handling

Function sst_acpi_probe() uses plain strcpy for setting member firmware_name
of a struct intel_sst_drv from member firmware of a struct sst_machines.
Thereby the destination array has got a length of 20 byte while the source may
hold 32 byte. Since eg. commit 64b9c90b86 ("ASoC: Intel: Fix BYTCR firmware
name") increased strings from "fw_sst_0f28.bin" to "intel/fw_sst_0f28.bin"
there is an actual possibility that the 20 byte array at the end of struct
intel_sst_drv is overrun.

Thus increase the size of the destination and use the same define for both
structs. Detected by Coverity CID 1260087.

Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

sound/soc/intel/sst/sst.h

@@ -58,6 +58,7 @@ enum sst_algo_ops {
 #define SST_BLOCK_TIMEOUT	1000
 
 #define FW_SIGNATURE_SIZE	4
+#define FW_NAME_SIZE		32
 
 /* stream states */
 enum sst_stream_states {
@@ -426,7 +427,7 @@ struct intel_sst_drv {
 	 * Holder for firmware name. Due to async call it needs to be
 	 * persistent till worker thread gets called
 	 */
-	char firmware_name[20];
+	char firmware_name[FW_NAME_SIZE];
 };
 
 /* misc definitions */

sound/soc/intel/sst/sst_acpi.c

@@ -47,7 +47,7 @@ struct sst_machines {
 	char board[32];
 	char machine[32];
 	void (*machine_quirk)(void);
-	char firmware[32];
+	char firmware[FW_NAME_SIZE];
 	struct sst_platform_info *pdata;
 
 };