sys: fsext: FspFsextProviderTransact

opt/fsext/inc/winfsp/fsext.h

@@ -53,6 +53,9 @@ typedef struct
 
 FSP_DDI_DEF(NTSTATUS, FspFsextProviderRegister,
     FSP_FSEXT_PROVIDER *Provider)
+FSP_DDI_DEF(NTSTATUS, FspFsextProviderTransact,
+    PDEVICE_OBJECT DeviceObject, PFILE_OBJECT FileObject,
+    FSP_FSCTL_TRANSACT_RSP *Response, FSP_FSCTL_TRANSACT_REQ **PRequest)
 
 FSP_DDI_DEF(NTSTATUS, FspPosixMapUidToSid,
     UINT32 Uid,

src/sys/fsext.c

@@ -132,3 +132,56 @@ NTSTATUS FspFsextProviderRegister(FSP_FSEXT_PROVIDER *Provider)
 
     return Result;
 }
+
+NTSTATUS FspFsextProviderTransact(PDEVICE_OBJECT DeviceObject, PFILE_OBJECT FileObject,
+    FSP_FSCTL_TRANSACT_RSP *Response, FSP_FSCTL_TRANSACT_REQ **PRequest)
+{
+    /*
+     * This function uses IoBuildDeviceIoControlRequest to build an IRP and then send it
+     * to the WinFsp driver. IoBuildDeviceIoControlRequest places the IRP in the IRP queue
+     * thus allowing it to be cancelled with CancelSynchronousIo.
+     *
+     * Special kernel APC's must be enabled:
+     * See https://www.osr.com/blog/2018/02/14/beware-iobuilddeviceiocontrolrequest/
+     */
+    ASSERT(!KeAreAllApcsDisabled());
+
+    NTSTATUS Result;
+    IO_STATUS_BLOCK IoStatus;
+    PIRP Irp;
+    PIO_STACK_LOCATION IrpSp;
+
+    if (0 != PRequest)
+        *PRequest = 0;
+
+    if (0 == DeviceObject)
+        DeviceObject = IoGetRelatedDeviceObject(FileObject);
+
+    Irp = IoBuildDeviceIoControlRequest(FSP_FSCTL_TRANSACT_INTERNAL,
+        DeviceObject,
+        Response,
+        0 != Response ? Response->Size : 0,
+        PRequest,
+        0 != PRequest ? sizeof(PVOID) : 0,
+        FALSE,
+        0,
+        &IoStatus);
+    if (0 == Irp)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    /*
+     * IoBuildDeviceIoControlRequest builds an IOCTL IRP without a FileObject.
+     * Patch it so that it is an FSCTL IRP with a FileObject. Mark it as
+     * IRP_SYNCHRONOUS_API so that CancelSynchronousIo can cancel it.
+     */
+    Irp->Flags |= IRP_SYNCHRONOUS_API;
+    IrpSp = IoGetNextIrpStackLocation(Irp);
+    IrpSp->MajorFunction = IRP_MJ_FILE_SYSTEM_CONTROL;
+    IrpSp->MinorFunction = IRP_MN_USER_FS_REQUEST;
+    IrpSp->FileObject = FileObject;
+
+    Result = IoCallDriver(DeviceObject, Irp);
+    ASSERT(STATUS_PENDING != Result);
+
+    return Result;
+}