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/*++
Copyright (c) 1999 - 2002 Microsoft Corporation
Module Name:
operations.c
Abstract:
This is the support routines module of the kernel mode filter driver implementing
filter metadata management.
Environment:
Kernel mode
--*/
#include "pch.h"
//
// Assign text sections for each routine.
//
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, FmmAllocateUnicodeString)
#pragma alloc_text(PAGE, FmmFreeUnicodeString)
#pragma alloc_text(PAGE, FmmTargetIsVolumeOpen)
#pragma alloc_text(PAGE, FmmIsImplicitVolumeLock)
#endif
//
// Support Routines
//
NTSTATUS
FmmAllocateUnicodeString (
_Inout_ PUNICODE_STRING String
)
/*++
Routine Description:
This routine allocates a unicode string
Arguments:
String - supplies the size of the string to be allocated in the MaximumLength field
return the unicode string
Return Value:
STATUS_SUCCESS - success
STATUS_INSUFFICIENT_RESOURCES - failure
--*/
{
PAGED_CODE();
String->Buffer = ExAllocatePoolZero( PagedPool,
String->MaximumLength,
FMM_STRING_TAG );
if (String->Buffer == NULL) {
DebugTrace( DEBUG_TRACE_ERROR,
("[Fmm]: Failed to allocate unicode string of size 0x%x\n",
String->MaximumLength) );
return STATUS_INSUFFICIENT_RESOURCES;
}
String->Length = 0;
return STATUS_SUCCESS;
}
VOID
FmmFreeUnicodeString (
_Inout_ PUNICODE_STRING String
)
/*++
Routine Description:
This routine frees a unicode string
Arguments:
String - supplies the string to be freed
Return Value:
None
--*/
{
PAGED_CODE();
ExFreePoolWithTag( String->Buffer,
FMM_STRING_TAG );
String->Length = String->MaximumLength = 0;
String->Buffer = NULL;
}
BOOLEAN
FmmTargetIsVolumeOpen (
_In_ PFLT_CALLBACK_DATA Cbd
)
/*++
Routine Description:
This routine returns if the target object in this callback datastructure
is a volume. If the file object is NULL then assume this is NOT a volume
file object
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
Return Value:
TRUE - target is a volume
FALSE - target is not a volume
--*/
{
PAGED_CODE();
if ((Cbd->Iopb->TargetFileObject != NULL) &&
FlagOn( Cbd->Iopb->TargetFileObject->Flags, FO_VOLUME_OPEN )) {
return TRUE;
} else {
return FALSE;
}
}
NTSTATUS
FmmIsImplicitVolumeLock(
_In_ PFLT_CALLBACK_DATA Cbd,
_Out_ PBOOLEAN IsLock
)
/*++
Routine Description:
This routine determines if an open is a implicit volume lock.
Arguments
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
IsLock - Supplies a pointer to a user allocated boolean
which is used to tell the user whether the
operation is an implied volume lock.
Return Value:
Returns STATUS_SUCCESS if the the function determined whether or not
the operation was a volume lock. On STATUS_SUCCESS it is safe to check
IsLock to get the answer. Otherwise, the check failed and we don't know
if it is a lock or not. STATUS_INVALID_PARAMETER indicates that the
volume's file system type is unrecognized by the check function. This is
an error code.
--*/
{
NTSTATUS status = STATUS_SUCCESS;
PFMM_INSTANCE_CONTEXT instanceContext = NULL;
USHORT shareAccess;
PAGED_CODE();
//
// Get the instance context so we know
// which file system we are attached to.
//
status = FltGetInstanceContext( Cbd->Iopb->TargetInstance,
&instanceContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_METADATA_OPERATIONS,
("[Fmm]: FmmIsImplicitVolumeLock -> Failed to get instance context.\n") );
goto FmmIsImplicitVolumeLockCleanup;
}
FLT_ASSERT( instanceContext != NULL );
//
// Now check to see if the open is an implicit volume lock. It is if the
// caller doesn't want to allow other handles on the volume to be open for
// write and/or delete (i.e. they must be read-only). We must close our
// handle to our metadata file so that the volume open can succeed.
//
shareAccess = Cbd->Iopb->Parameters.Create.ShareAccess;
#pragma warning( push )
#pragma warning( disable: 4061 )
switch (instanceContext->FilesystemType) {
case FLT_FSTYPE_REFS:
case FLT_FSTYPE_NTFS:
case FLT_FSTYPE_FAT:
*IsLock = (!BooleanFlagOn( shareAccess, FILE_SHARE_WRITE | FILE_SHARE_DELETE));
status = STATUS_SUCCESS;
break;
default:
status = STATUS_INVALID_PARAMETER;
break;
}
#pragma warning( pop )
FmmIsImplicitVolumeLockCleanup:
if (instanceContext != NULL ) {
FltReleaseContext( instanceContext );
}
return status;
}
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