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

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Message-Id: <200910242340.n9ONe98E031918@bari.maths.usyd.edu.au>
Date: Sun, 25 Oct 2009 10:40:09 +1100
From: psz@...hs.usyd.edu.au
To: pavel@....cz
Cc: bugtraq@...urityfocus.com, dan@...htwave.net.ru
Subject: Re: /proc filesystem allows bypassing directory permissions on Linux

Dear Pavel,

> ... that's exactly the problem.

I see, the /proc/*/fd/* objects seem "confused": are they symlinks,
hardlinks, or open file descriptors? I guess should always act as
the latter, where access mode flags (O_RDONLY or O_RDWR) are set at
open() and not changeable afterwards in fcntl(). Any open() on them
should behave as a dup().

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