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How to query Device Instance Id in minifilter ?

Nikhil_V_SNikhil_V_S Member - All Emails Posts: 58

I have created a file system mini-filter to filter the file operations.
Now I have created a function to find the Instance Path of USB Storage Device.but it causes the crash of mini-filter.
Following block of code is used for Querying Instance Path.

    NTSTATUS CheckPNPID( PDEVICE_OBJECT pdo )
    {
        DEVPROPKEY propertyKey = DEVPKEY_Device_InstanceId;
        ULONG bufferLength = 100; // Hopefully big enough size
        PVOID pDevicePropertyData;
        DEVPROPTYPE devicePropertydataType;
        ULONG returnedLength;
        NTSTATUS status=STATUS_SUCCESS;

        pDevicePropertyData = ExAllocatePoolWithTag(NonPagedPool, bufferLength, NL_POOL_TAG_NIK);
        if (pDevicePropertyData == NULL) {
            DbgPrint("MINIFILTER  :CheckPNPID ExAllocatePoolWithTag  pDevicePropertyData==NULL");
            return(status);
        }

        status = IoGetDevicePropertyData(
            pdo, // PhysicalDeviceObject
            &propertyKey,
            LOCALE_NEUTRAL,
            0,
            bufferLength,
            pDevicePropertyData,
            &returnedLength,
            &devicePropertydataType
            );

        if (status != STATUS_SUCCESS && status != STATUS_BUFFER_TOO_SMALL) {
            DbgPrint("MINIFILTER  :CheckPNPID IoGetDevicePropertyData  status!=STATUS_SUCCESS 1");
            return(status);
        }
        if (status == STATUS_BUFFER_TOO_SMALL) {
            ExFreePoolWithTag(pDevicePropertyData, NL_POOL_TAG_NIK); 
            bufferLength = returnedLength;
            pDevicePropertyData = ExAllocatePoolWithTag(NonPagedPool, bufferLength, NL_POOL_TAG_NIK);
            if (pDevicePropertyData == NULL) {
                DbgPrint("MINIFILTER  :CheckPNPID ExAllocatePoolWithTag  pDevicePropertyData==NULL 2");
                return(status);
            }
            status = IoGetDevicePropertyData(
                pdo, // PhysicalDeviceObject
                &propertyKey,
                LOCALE_NEUTRAL,
                0,
                bufferLength,
                pDevicePropertyData,
                &returnedLength,
                &devicePropertydataType
                );
            if (status != STATUS_SUCCESS) {
                DbgPrint("MINIFILTER  :CheckPNPID Using IOGETDEVICEPROPERTY  failed");
                return(status);
            }
            else
            {
                DbgPrint("MINIFILTER  :CheckPNPID Using IOGETDEVICEPROPERTY  success 2");
            }
        }
        if(status==STATUS_SUCCESS)
        {
            DbgPrint("MINIFILTER :CheckPNPID Using IOGETDEVICEPROPERTY  success");
        }
        return(status);
    }

``````````````````````````
I am using WDK 8.0 and build a 32-bit driver. Is the above code wrong?

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