[cifs-protocol] SMB1 Trans2SetPathInfo() FileEndOfFileInformation is not enforcing share modes

Bill Wesse billwe at microsoft.com
Wed Nov 25 12:01:42 MST 2009

Jeremy, I agree with you concerning Windows behavior needing to be documented; but I felt it necessary to mention the possibilities concerning further elaboration - since I am not the one to make that decision (nor do I wish to second guess those who do).

My next step is to finish tracking down file handle visibility within the server, and how that applies to pass-through versus no pass-through: as you noted, there are certainly differences, the main one concerning why pass-through doesn't honor the share mode.

My first take on this is to assume pass-through obtains the existing handle (making it safe to set the size); but I have not yet confirmed this (or proven it wrong - in which case I would be intensely bothered by the behavior, which would have the implication of corrupting the state of file state under the original handle).

Either way, I do intend to file a TDI on the topic, once I finish the code study; I also intend to set up test code to exercise the information levels against the SMB calls.

Bill Wesse
MCSE, MCTS / Senior Escalation Engineer, US-CSS DSC PROTOCOL TEAM
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-----Original Message-----
From: Jeremy Allison [mailto:jra at samba.org] 
Sent: Wednesday, November 25, 2009 1:46 PM
To: Bill Wesse
Cc: Tim Prouty; pfif at tridgell.net; cifs-protocol at samba.org
Subject: Re: [cifs-protocol] SMB1 Trans2SetPathInfo() FileEndOfFileInformation is not enforcing share modes

On Wed, Nov 25, 2009 at 05:14:26PM +0000, Bill Wesse wrote:
> Hello Tim. I think the difference in the response between the standard versus pass-through level lies in how the file handle is obtained during the call (given that TRANS2_SET_PATH_INFORMATION passes the path, and not the handle). The logical conclusion from the trace is that pass-through gets the existing handle, and the non pass-through value simply fails, because a new handle cannot be opened due to the lack of sharing.
> I will continue my investigation into the details on the differences between the base & pass-through handling, with respect to the file path / handle source. Pass-through is basically implementation dependent, as noted in [MS-FSCC] (reference below), so there is a possibility this may not be further elaborated on in the documents.

That won't wash I'm afraid. If it's visible on the wire, and it
changes the visible behaviour of the file server, then it needs
to get documented.


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