bugtraq - Re: Changes to the filesystem while find is running

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Date: Wed, 24 Nov 2004 07:22:33 +1100 (EST)
From: psz@...hs.usyd.edu.au (Paul Szabo)
To: Martin.Buchholz@....COM
Cc: srevilak@...akeasy.net, bugtraq@...ession.spiral-arm.org,
	parimiv@...haw.com, levon@...ementarian.org,
	bugtraq@...urityfocus.com, bug-findutils@....org
Subject: Re: Changes to the filesystem while find is running - comments?

Martin Buchholz <Martin.Buchholz@....COM> wrote:

>> I think find should never cause an automount to "trigger" and cause it to
>> be mounted. It is OK to traverse if it was mounted to start with; is surely
>> not OK to traverse if it wasn't already mounted. ...
>> [Right now cannot think of examples where find causing automounts to
>> trigger would be an obvious security or performance issue.]
> 
> I strongly disagree with this principle.  Automount points (at least on
> Solaris) are supposed to be transparent to the user; just an
> implementation optimization over having them permanently mounted.

Can some BugTraq-er help me here please: give an example where triggering
an automount has security implications? [Can a security compromise of the
mountee compromise the security of the automount machine? Does it make a
difference if the automount is triggered by a "plain" user access or a
rootly one, or are there ever mountpoints that only root has access to?]

What do you mean by automounts being an optimization? I would have thought
that permanent mounts are less resource-demanding than active mounting and
expiring; I thought that automounts were a convenience when the mountee may
not be permanently available.

Would find triggering automounts impact performance? Would it cause delays
or blocks if the mountee was not online?

Cheers,

Paul Szabo - psz@...hs.usyd.edu.au  http://www.maths.usyd.edu.au:8000/u/psz/
School of Mathematics and Statistics  University of Sydney   2006  Australia