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

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Date: Tue, 23 Nov 2004 20:47:38 -0500 (EST)
From: Steve  Revilak <srevilak@...akeasy.net>
To: Tim Nelson <security@...alive.biz>
Cc: James Youngman <bugtraq@...ession.spiral-arm.org>, parimiv@...haw.com,
	martin.buchholz@....com, levon@...ementarian.org,
	bugtraq@...urityfocus.com, bug-findutils@....org
Subject: Re: Changes to the filesystem while find is running - comments?


> On Mon, 22 Nov 2004, James Youngman wrote:
>
> > I have run into a problem as of findutils-4.2.7.  This is simply that
> > there seem to be cases where automountd on Solaris works by exchanging
> > one mounted filesystem for another.  I could support/allow this

> From: Tim Nelson

>  	Under what sort of conditions are the filesystems exchanged?
> Whenever it feels like it?  Or are there conditions under which this
> happens?  (I'm just thinking that maybe, by knowing the conditions, we'll
> be able to come up with another useful check).

This is what I've been able to determine through observation of
automounted directories on Solaris 8.

For the sake of example let's say that /mount is the root directory
for an automounter map.  /mount/<subdir> are the individual mount
points within the automounter map.

  * / has device no. R

  * /mount has device number X (where X != R).  X doesn't seem to
    change.

  * /mount/SUBDIR has device number X when not mounted (same device
    number as /mount)

  * /mount/SUBDIR has device number Y when mounted (where Y != X)

  * Unlike some automounter implementations, the directory
    /mount/SUBDIR will not disappear when /mount/SUBDIR becomes
    unmounted.  Nor will it disappear when the automounter exits.
    /mount/SUBDIR is created when the automounter starts.

  * If /mount/SUBDIR is not mounted, accessing /mount/SUBDIR does not
    trigger a mount.

  * If /mount/SUBDIR is not mounted, accessing /mount/SUBDIR/. does
    trigger a mount.


With other automounter implementations (Fedora core 1 & 2, Mac OSX
10.3), a mount will be triggered merely by accessing /mount/SUBDIR (as
opposed to /mount/SUBDIR/.).  These cases don't pose a problem -- as
far as find is concerned, it sees the device number after the mount
has occurred.

-- 
Steve