Redirecting FS filter and relative CREATE

NTFSD
1

RE: [ntfsd] RE: IRQL in FSD/Filter driver Hi all,

I’m writing an FS filter which sometimes redirects the CREATE requests to
the other file by updating the FileObject->FileName and returning
STATUS_REPARSE.
What if I would get relative CREATE with FileObject->RelatedFileObject is
not NULL?
The redirected file name has nothing to do with the related file object.
Must I set FileObject->RelatedFileObject to NULL before returning
STATUS_REPARSE? Must I call ObDereferenceObject on it before setting to
NULL?

Max

2

RelatedFileObject is referenced by ObOpenObjectByName
(before IopParseFile is actually called) so you do not need
to dereference it. It is used only in IRP_MJ_CREATE request.
This field in file object is invalid anytime after create has completed.

If you want to redirect the create request you can empty the
FO->RelatedFileObject, but you must then provide
full path name in FO->FileName (from the volume root).

Paul

-----P?vodn? zpr?va-----
Od: Maxim S. Shatskih [SMTP:xxxxx@storagecraft.com]
Odesl?no: 20. ?ervna 2000 0:28
Komu: File Systems Developers
P?edm?t: [ntfsd] Redirecting FS filter and relative CREATE

RE: [ntfsd] RE: IRQL in FSD/Filter driver Hi all,

I’m writing an FS filter which sometimes redirects the CREATE requests to
the other file by updating the FileObject->FileName and returning
STATUS_REPARSE.
What if I would get relative CREATE with FileObject->RelatedFileObject is
not NULL?
The redirected file name has nothing to do with the related file object.
Must I set FileObject->RelatedFileObject to NULL before returning
STATUS_REPARSE? Must I call ObDereferenceObject on it before setting to
NULL?

Max

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3

Hi,

If I replace FO->FileName with my new file name,
who will free the memory of original FO->FileName?

Regards

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Pavel Hrdina
Sent: Tuesday, June 20, 2000 8:54 AM
To: File Systems Developers
Subject: [ntfsd] RE: Redirecting FS filter and relative CREATE

RelatedFileObject is referenced by ObOpenObjectByName
(before IopParseFile is actually called) so you do not need
to dereference it. It is used only in IRP_MJ_CREATE request.
This field in file object is invalid anytime after create has completed.

If you want to redirect the create request you can empty the
FO->RelatedFileObject, but you must then provide
full path name in FO->FileName (from the volume root).

Paul

> -----P?vodn? zpr?va-----
> Od: Maxim S. Shatskih [SMTP:xxxxx@storagecraft.com]
> Odesl?no: 20. ?ervna 2000 0:28
> Komu: File Systems Developers
> P?edm?t: [ntfsd] Redirecting FS filter and relative CREATE
>
> RE: [ntfsd] RE: IRQL in FSD/Filter driver Hi all,
>
> I’m writing an FS filter which sometimes redirects the CREATE
requests to
> the other file by updating the FileObject->FileName and returning
> STATUS_REPARSE.
> What if I would get relative CREATE with
FileObject->RelatedFileObject is
> not NULL?
> The redirected file name has nothing to do with the related file object.
> Must I set FileObject->RelatedFileObject to NULL before returning
> STATUS_REPARSE? Must I call ObDereferenceObject on it before setting to
> NULL?
>
> Max
>
>
> —
> You are currently subscribed to ntfsd as: xxxxx@sodatsw.cz
> To unsubscribe send a blank email to $subst(‘Email.Unsub’)

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4

> If I replace FO->FileName with my new file name,

who will free the memory of original FO->FileName?

You, by ExFreePool.
It is allocated in the IO manager by ExAllocatePoolWithTag(PagedPool…,
‘mNoI’)

Max