ProbeForWrite routine
The ProbeForWrite routine checks that a user-mode buffer actually resides in the user-mode portion of the address space, is writable, and is correctly aligned.
Syntax
VOID ProbeForWrite( __inout PVOID Address, __in SIZE_T Length, __in ULONG Alignment );
Parameters
- Address [in, out]
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Specifies the beginning of the user-mode buffer.
- Length [in]
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Specifies the length, in bytes, of the user-mode buffer.
- Alignment [in]
-
Specifies the required alignment, in bytes, of the beginning of the user-mode buffer.
Return value
None
Remarks
If the specified range of memory is not a valid user-mode address range or is not writable (no access, read-only, and so on), ProbeForWrite raises the STATUS_ACCESS_VIOLATION exception. If the beginning of the address range is not aligned on the byte boundary that is specified by Alignment, ProbeForWrite raises the STATUS_DATATYPE_MISALIGNMENT exception.
Kernel-mode drivers must use ProbeForWrite to validate write access to buffers allocated in user space. It is most commonly used during METHOD_NEITHER I/O to validate the user buffer pointed to by Irp->UserBuffer.
Drivers must call ProbeForWrite inside a try/except block. If the routine raises an exception, the driver should complete the IRP with the appropriate error. Note that subsequent accesses by the driver to the user-mode buffer must also be encapsulated within a try/except block: a malicious application could have another thread deleting, substituting, or changing the protection of user address ranges at any time (even after or during a call to ProbeForRead or ProbeForWrite). For more information, see Handling Exceptions.
Do not use this routine on kernel-mode addresses; it will raise an exception.
If Irp->RequestorMode = KernelMode, the Irp->AssociatedIrp.SystemBuffer and Irp->UserBuffer fields do not contain user-mode addresses, and a call to ProbeForWrite to probe a buffer pointed to by either field will raise an exception.
Requirements
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Version | Available in Windows 2000 and later versions of Windows. |
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IRQL | <= APC_LEVEL |
See also
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Build date: 4/2/2012
