Add extra tests to the MassStorage device demo and class driver for validating command blocks from the host.

Demos/Device/LowLevel/MassStorage/MassStorage.c

@@ -256,6 +256,8 @@ static bool ReadInCommandBlock(void)
 	/* Verify the command block - abort if invalid */
 	if ((CommandBlock.Signature         != CBW_SIGNATURE) ||
 	    (CommandBlock.LUN               >= TOTAL_LUNS)    ||
+		(CommandBlock.Flags              & 0x1F)          ||
+		(CommandBlock.SCSICommandLength == 0)             ||
 		(CommandBlock.SCSICommandLength >  MAX_SCSI_COMMAND_LENGTH))
 	{
 		/* Stall both data pipes until reset by host */

LUFA/Drivers/USB/Class/Device/MassStorage.c

@@ -149,6 +149,8 @@ static bool MS_Device_ReadInCommandBlock(USB_ClassInfo_MS_Device_t* const MSInte
 
 	if ((MSInterfaceInfo->State.CommandBlock.Signature         != MS_CBW_SIGNATURE)                  ||
 	    (MSInterfaceInfo->State.CommandBlock.LUN               >= MSInterfaceInfo->Config.TotalLUNs) ||
+		(MSInterfaceInfo->State.CommandBlock.Flags              & 0x1F)                              ||
+		(MSInterfaceInfo->State.CommandBlock.SCSICommandLength == 0)                                 ||
 		(MSInterfaceInfo->State.CommandBlock.SCSICommandLength >  16))
 	{
 		Endpoint_StallTransaction();