[jcifs] Curious "race" condition

Caldarale, Charles R Chuck.Caldarale at unisys.com
Fri Oct 22 10:54:01 MDT 2010

> From: jcifs-bounces at lists.samba.org [mailto:jcifs-bounces at lists.samba.org] On Behalf Of André Warnier
> Subject: Re: [jcifs] Curious "race" condition

> I was just wondering if somehow, even if extremely unlikely, 
> there could be some small window of time while program A was 
> in the process of renaming the file across a SMB share, and
> process B is reading that same directory and opening that file,
> where program B /could/ find a directory entry associated to a
> zero-size file.

We have customers doing essentially the same thing, albeit with our own proprietary SMB server, not Samba.

Would it be possible to send me a Wireshark or tcpdump capture of the renaming portion of the process?  I'd like to see the exact sequence of SMB commands sent over the wire, and I could then look in the Samba source to see how it interprets them (and compare that with what we do on our platform).

Assuming Samba is doing a true rename, there should be no window where the file size appears to be zero.  However, if it's implemented as a copy and delete, there would be.

 - Chuck

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