sfc: Support variable-length response to MCDI GET_BOARD_CFG

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/mcdi.c

@@ -683,12 +683,14 @@ int efx_mcdi_get_board_cfg(struct efx_nic *efx, u8 *mac_address,
 	if (mac_address)
 		memcpy(mac_address, outbuf + offset, ETH_ALEN);
 	if (fw_subtype_list) {
+		/* Byte-swap and truncate or zero-pad as necessary */
 		offset = MC_CMD_GET_BOARD_CFG_OUT_FW_SUBTYPE_LIST_OFST;
 		for (i = 0;
-		     i < MC_CMD_GET_BOARD_CFG_OUT_FW_SUBTYPE_LIST_MINNUM;
+		     i < MC_CMD_GET_BOARD_CFG_OUT_FW_SUBTYPE_LIST_MAXNUM;
 		     i++) {
 			fw_subtype_list[i] =
-				le16_to_cpup((__le16 *)(outbuf + offset));
+				(offset + 2 <= outlen) ?
+				le16_to_cpup((__le16 *)(outbuf + offset)) : 0;
 			offset += 2;
 		}
 	}

drivers/net/ethernet/sfc/mtd.c

@@ -627,7 +627,8 @@ static int siena_mtd_get_fw_subtypes(struct efx_nic *efx,
 				     struct efx_mtd *efx_mtd)
 {
 	struct efx_mtd_partition *part;
-	uint16_t fw_subtype_list[MC_CMD_GET_BOARD_CFG_OUT_FW_SUBTYPE_LIST_MINNUM];
+	uint16_t fw_subtype_list[
+		MC_CMD_GET_BOARD_CFG_OUT_FW_SUBTYPE_LIST_MAXNUM];
 	int rc;
 
 	rc = efx_mcdi_get_board_cfg(efx, NULL, fw_subtype_list, NULL);