firewire: sbp2: fix status reception

Per SBP-2 clause 5.3, a target shall store 8...32 bytes of status
information.  Trailing zeros after the first 8 bytes don't need to be
stored, they are implicit.  Fix the status write handler to clear all
unwritten status data.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/sbp2.c

@@ -425,19 +425,20 @@ static void sbp2_status_write(struct fw_card *card, struct fw_request *request,
 	struct sbp2_logical_unit *lu = callback_data;
 	struct sbp2_orb *orb;
 	struct sbp2_status status;
-	size_t header_size;
 	unsigned long flags;
 
 	if (tcode != TCODE_WRITE_BLOCK_REQUEST ||
-	    length == 0 || length > sizeof(status)) {
+	    length < 8 || length > sizeof(status)) {
 		fw_send_response(card, request, RCODE_TYPE_ERROR);
 		return;
 	}
 
-	header_size = min(length, 2 * sizeof(u32));
-	fw_memcpy_from_be32(&status, payload, header_size);
-	if (length > header_size)
-		memcpy(status.data, payload + 8, length - header_size);
+	status.status  = be32_to_cpup(payload);
+	status.orb_low = be32_to_cpup(payload + 4);
+	memset(status.data, 0, sizeof(status.data));
+	if (length > 8)
+		memcpy(status.data, payload + 8, length - 8);
+
 	if (STATUS_GET_SOURCE(status) == 2 || STATUS_GET_SOURCE(status) == 3) {
 		fw_notify("non-orb related status write, not handled\n");
 		fw_send_response(card, request, RCODE_COMPLETE);