WdfRequestProbeAndLockUserBufferForWrite function (wdfrequest.h)

Article
04/18/2022

[Applies to KMDF only]

The WdfRequestProbeAndLockUserBufferForWrite method verifies that an I/O request's user-mode buffer is writeable, and then it locks the buffer's physical memory pages so drivers in the driver stack can write into the buffer.

Syntax

NTSTATUS WdfRequestProbeAndLockUserBufferForWrite(
  [in]  WDFREQUEST Request,
  [in]  PVOID      Buffer,
  [in]  size_t     Length,
  [out] WDFMEMORY  *MemoryObject
);

Parameters

[in] Request

A handle to a framework request object.

[in] Buffer

A pointer to the request's output buffer. For more information, see the following Remarks section.

[in] Length

The length, in bytes, of the request's output buffer.

[out] MemoryObject

A pointer to a location that receives a handle to a framework memory object that represents the user output buffer.

Return value

WdfRequestProbeAndLockUserBufferForWrite returns STATUS_SUCCESS if the operation succeeds. Otherwise, this method might return one of the following values:

Return code	Description
STATUS_INVALID_PARAMETER	An input parameter is invalid.
STATUS_INVALID_USER_BUFFER	The Length parameter is zero.
STATUS_INVALID_DEVICE_REQUEST	The request has already been completed or is otherwise invalid.
STATUS_ACCESS_VIOLATION	The current thread is not the creator of the I/O request.
STATUS_INSUFFICIENT_RESOURCES	There is insufficient memory to complete the operation.

This method might also return other NTSTATUS values.

A bug check occurs if the driver supplies an invalid object handle.

Remarks

The user output buffer typically receives information that the driver has read from the device.

Only a top-level driver can call the WdfRequestProbeAndLockUserBufferForWrite method, because the method requires the process context of the process that created the I/O request.

The user-mode buffer that the Buffer parameter specifies can be the buffer that WdfRequestRetrieveUnsafeUserOutputBuffer retrieves, or it can be a different user-mode output buffer. For example, an I/O control code that uses the buffered access method might pass a structure that contains an embedded pointer to a user-mode buffer. In such a case, the driver can useWdfRequestProbeAndLockUserBufferForWrite to obtain a memory object for the buffer.

The buffer length that the Length parameter specifies must not be larger than the buffer's actual size. Otherwise, drivers can access memory outside of the buffer, which is a security risk.

If WdfRequestProbeAndLockUserBufferForWrite returns STATUS_SUCCESS, the driver receives a handle to a framework memory object that represents the user-mode buffer. To access the buffer, the driver must call WdfMemoryGetBuffer.

The framework memory object is automatically released when the driver calls WdfRequestComplete.

For more information about WdfRequestProbeAndLockUserBufferForWrite, see Accessing Data Buffers in Framework-Based Drivers.

Examples

For a code example that uses WdfRequestProbeAndLockUserBufferForWrite, see WdfRequestProbeAndLockUserBufferForRead.

Requirements

Requirement	Value
Target Platform	Universal
Minimum KMDF version	1.0
Header	wdfrequest.h (include Wdf.h)
Library	Wdf01000.sys (see Framework Library Versioning.)
IRQL	PASSIVE_LEVEL
DDI compliance rules	DriverCreate(kmdf), InvalidReqAccess(kmdf), InvalidReqAccessLocal(kmdf), KmdfIrql(kmdf), KmdfIrql2(kmdf), KmdfIrqlExplicit(kmdf)

Share via