SYSTEM_OBJECT_INFORMATION

The SYSTEM_OBJECT_INFORMATION structure (formally _SYSTEM_OBJECT_INFORMATION) is an irregularly recurring element in what a successful call to ZwQuerySystemInformation or NtQuerySystemInformation produces in its output buffer when given the information class SystemObjectInformation (0x11). The output begins with a SYSTEM_OBJECTTYPE_INFORMATION. There can be, and typically are, more of these throughout the buffer, but irregularly because each can be followed by any number of SYSTEM_OBJECT_INFORMATION structures. These too are irregularly spaced because although each is fixed in size, each is followed in turn by a variable-size Unicode string.

Documentation Status

The SYSTEM_OBJECT_INFORMATION structure is not documented.

Microsoft does publish the practical equivalent of a C-language definition as type information in symbol files—not for the kernel, where the structure is prepared, nor even for low-level user-mode DLLs that interpret the structure, but for a handful of higher-level DLLs that might ordinarily be thought very distant from any involvement with the structure. Perhaps only by oversight, but starting as long ago as Windows 8, Microsoft’s downloadable packages of public symbols have included a smattering of private symbol files and these continue to be available through the public symbol server. Precisely which DLLs have the type information varies between versions. COMBASE.DLL is among the more reliable nowadays. Disclosure in symbol files for URLMON.DLL stopped for the 1803 release of Windows 10 but is specially notable because of this DLL’s origins in Internet Explorer and thence for the strong suggestion that Microsoft’s programmers of Internet Explorer had access to more details of low-level Windows programming than Microsoft publishes for wider use (including by the programmers of competing web browsers).

Type information for the structure has also seeped out at the other end of the Windows timeline, though not in symbol files but in statically linked libraries: GDISRVL.LIB from the Device Driver Kit (DDK) for Windows NT 3.51; and SHELL32.LIB from the DDK for Windows NT 4.0.

Layout

The SYSTEM_OBJECT_INFORMATION is 0x30 or 0x50 bytes in 32-bit and 64-bit Windows, respectively.

ULONG NextEntryOffset;

PVOID Object;

PVOID CreatorUniqueProcess;

USHORT CreatorBackTraceIndex;

ULONG Flags;

USHORT Flags;

LONG PointerCount;

LONG HandleCount;

ULONG PagedPoolCharge;

ULONG NonPagedPoolCharge;

PVOID ExclusiveProcessId;

PVOID SecurityDescriptor;

OBJECT_NAME_INFORMATION NameInfo;