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Invariant MDL Checking for Driver

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The Invariant MDL Checking for Driver option monitors how the driver handles invariant MDL buffers on a per-driver basis. This option detects illegal modification of invariant MDL buffers. To use this option, you must enable I/O Verification on at least one driver.

Note  This option is available starting with Windows 8.

The Invariant MDL Checking for Driver option performs a more intensive form of the invariant MDL checking than the Invariant MDL Checking for Stack option. When the Invariant MDL Checking for Driver is active, buffer invariance is validated across every call to the IoCallDriver and IoCompleteRequest routines.

Every time a new invariant MDL buffer is seen with an IRP, Driver Verifier computes a signature for the buffer contents and stores it in its internal database. When Driver Verifier encounters an invariant MDL buffer that it has seen earlier, it will validate that the contents of buffer has not changed, by comparing the signature in the database with the signature computed over current invariant MDL buffer contents.

This option is global and cannot be enforced selectively some drivers.

Activating this option

You can activate the Invariant MDL Checking for Driver feature for one or more drivers by using Driver Verifier Manager or the Verifier.exe command line. For details, see Selecting Driver Verifier Options. You must restart the computer to activate or deactivate the Invariant MDL Checking for Driver option.

To activate the Invariant MDL Checking for Stack option, you must also activate I/O Verification.

  • At the command line

    At the command line, the Invariant MDL Checking for Driver is represented by verifier /flags 0x00004000 (Bit 14). To activate Invariant MDL Checking for Driver, use a flag value of 0x00004010 or add 0x00004010 to the flag value. This value activates I/O Verification (0x10) and the Invariant MDL Checking for Driver (0x00004000). For example:

    verifier /flags 0x00004010 /driver MyDriver.sys

    The feature will be active after the next boot.

  • Using Driver Verifier Manager

    1. Start Driver Verifier Manager. Type Verifier in a Command Prompt window.
    2. Select Create custom settings (for code developers) and then click Next.
    3. Select Select individual settings from a full list.
    4. Select (check)I/O Verification and Invariant MDL Checking for Driver.
    5. Restart the computer.