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Is section context referenced in SectionNotificationCallback ?

Sergey_PisarevSergey_Pisarev Member - All Emails Posts: 236

Hello!
I am using FltCreateSectionForDataScan to read file. Now I want to implement SectionNotificationCallback to hold off conflicting io until I am done with the section.
In my worker thread when I finished with the section:
1) close section(ZwClose + ObDereferenceObject)
2) set notification event(located in section context) indicating that I am done with the section
3) call FltCloseSectionForDataScan + FltReleaseContext

If my SectionNotificationCallback gets called I wait for notification event(in section context) and return from SectionNotificationCallback. It is safe to do so if section context additionally referenced before SectionNotificationCallback. If no additional reference taken before SectionNotificationCallback I can wait on invalid memory (section context destroyed already).

Is my solution ok or I can’t assume additional reference in SectionNotificationCallback ?

Comments

  • Koby_KahaneKoby_Kahane Member Posts: 11

    The section conflict notification callback is called with the section context as an argument and it is guaranteed to remain valid while the callback is in progress.

    Note however that if all your conflict callback does is wait for the scanner to be finished, it is actually unnecessary. Filter Manager itself will wait for an existing section context to be closed and retry a conflicting I/O - basically doing the same thing you are doing with your notification event. This will occur even if you have a null callback. The callback can be used for logging or to prematurely terminate an ongoing scan, so a conflicting I/O operation can be retried more quickly.

  • Sergey_PisarevSergey_Pisarev Member - All Emails Posts: 236

    Thank you very much Koby.

    BTW I didn’t get email notification about Koby’s reply.

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