为什么会发生异常??天啊!!

我在filespy中加一个写例程,处理加密.我自己分配了一块内存在里面加密在完成例程中释放.

typedef struct _DOWN_TRANSFER{
   BOOLEAN  MemLock;
   PMDL    MdlAddress;
   PVOID    UserAddress;
} DOWN_TRANSFER, *PDOWN_TRANSFER;//头文件中定义

SpyWrite(
IN PDEVICE_OBJECT DeviceObject,
IN PIRP Irp
)
{
  PCHAR pBuffer;
  int i;
  int Length;
  PIO_STACK_LOCATION  IrpCurStack ;
  PDOWN_TRANSFER       yang;
  PFILE_OBJECT        FileObject;
    
  IrpCurStack=IoGetCurrentIrpStackLocation(Irp);
  Length = IrpCurStack->Parameters.Write.Length;
  pBuffer = ExAllocatePool(NonPagedPool,Length);
  FileObject = IrpCurStack->FileObject;

  if( Irp ->Flags & ( IRP_NOCACHE | IRP_PAGING_IO |   IRP_SYNCHRONOUS_PAGING_IO ) )
{
yang = ExAllocatePool( NonPagedPool, sizeof(DOWN_TRANSFER));
yang->MdlAddress  = Irp->MdlAddress;
yang->UserAddress = pBuffer;

if( Irp ->MdlAddress )
{
    RtlCopyMemory(pBuffer,MmGetSystemAddressForMdl(Irp->MdlAddress),Length);
}
else            
{
RtlCopyMemory(pBuffer,Irp->UserBuffer,Length);
}
  
if (NodeType(FileObject->FsContext) == FAT_NTC_FCB)//判断是不是文件内容
{  
for(i=0;i<(int)Length;
{
pBuffer=~pBuffer;
}
}
IoAllocateMdl(pBuffer, IrpCurStack->Parameters.Write.Length, FALSE, FALSE, Irp);

if (Irp->MdlAddress == NULL)
{
   //return NULL;    
}

__try
{
   MmProbeAndLockPages(Irp->MdlAddress, Irp->RequestorMode, IoWriteAccess);
}
__except (EXCEPTION_EXECUTE_HANDLER)
{
IoFreeMdl(Irp->MdlAddress);
Irp->MdlAddress = NULL;
}
}
IoSetCompletionRoutine( Irp , WriteCompleted ,(PVOID) yang ,TRUE ,FALSE ,FALSE );
return SpyPassThrough( DeviceObject , Irp );
}

WriteCompleted(
IN PDEVICE_OBJECT DeviceObject,
IN PIRP Irp,
IN PVOID Context
)
{
ULONG Length;
PCHAR pBuffer;
int i ;
PDOWN_TRANSFER       yang;
yang=(PDOWN_TRANSFER)Context;
 
MmUnlockPages(Irp->MdlAddress);
IoFreeMdl(Irp->MdlAddress);
Irp->MdlAddress  = yang->MdlAddress;
ExFreePool(yang->UserAddress);
ExFreePool(yang);

if( Irp->PendingReturned ) {
    IoMarkIrpPending( Irp );
    }
return  Irp->IoStatus.Status;
}

Softice有时会报下面的错误:
第一个错误：
Break Due to KeBugCheckEx(Unhandled mode exception)
Error=50 (PAGE_FAULT_NONPAGED_AREA)  P1=ED5E4400  P2=0  P3=ED4A3748   P4=0
第二个错误是：
Break Due to KeBugCheckEx(Unhandled mode exception)
Error=4E (PFN_LIST_CORRUPT) P1=7  P2=11  P3=8A50  P4=0

自己顶一下

检查一下dump文件，看看是不是你的代码的问题，看看栈里有没有什么有用的信息，在结合你的源码看看，应该能找出问题来的