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

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Message-Id: <200911032317.nA3NHDf6010572@bari.maths.usyd.edu.au>
Date: Wed, 4 Nov 2009 10:17:13 +1100
From: psz@...hs.usyd.edu.au
To: gombasg@...aki.hu, mrex@....com
Cc: bugtraq@...urityfocus.com, dan@...htwave.net.ru, jim@...n.com,
	marco@....nl, pavel@....cz
Subject: Re: /proc filesystem allows bypassing directory permissions on

>>> "mount --bind" behaves like a hard link and it does not increment the link
>>> count.
>
> # touch /tmp/a
> # mount --bind /etc/passwd /tmp/a
> # ls -l /etc/passwd
> -rw-r--r-- 1 root root 1990 2009-08-24 16:22 /etc/passwd
> ...
> Two references to the same inode, yet the link count is 1 and /proc is
> nowhere in the picture.

But, mount requires root (and root can do anything, including shooting
himself in the foot).

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