Memory leak of StreamHandle context

I have a problem of using minifilter.
I use StreamHandle context in pre-setinfo to store the target file name information of FileRenameInformation. The target file name buffer in StreamHandle context is allocated from NonPagedPool in pre-setinfo.
Then passed the context to CompletionContext. In the post-setinfo, call FltReleaseContext released the context. And the target file name buffer is released in the ContextRegistration.
Also, when FLTFL_POST_OPERATION_DRAINING flag is on, called the FltReleaseContext and return FLT_POSTOP_FINISHED_PROCESSING.
But sometimes get BSOD when using the verifier, and the dump file shows a memory leak problem when driver unload.

Sorry for my poor english. Can anyone help me?