bugtraq - Re: /proc filesystem allows bypassing directory permissions on Linux

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Date: Wed, 28 Oct 2009 07:39:45 +1100
From: psz@...hs.usyd.edu.au
To: dot@...at.at, matthew@...psky.org
Cc: bugtraq@...urityfocus.com, pavel@....cz
Subject: Re: /proc filesystem allows bypassing directory permissions on Linux

Tony Finch <dot@...at.at> wrote:

> According to POSIX, if you open the directory with O_SEARCH then openat()
> does not re-check search (+x) permissions.

My 2.6.26 kernel (or Debian lenny) does not seem to know about O_SEARCH.
But anyway... even if openat() does not re-check permissions, it should
surely fail when in fact it does not have permissions? Surely, directory
contents are not cached? Or, do you have an example (of a running OS)
where openat() succeeds without permissions?

Cheers, Paul

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