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

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Message-ID: <20091026104718.GD25340@elf.ucw.cz>
Date: Mon, 26 Oct 2009 11:47:18 +0100
From: Pavel Machek <pavel@....cz>
To: Dan Yefimov <dan@...htwave.net.ru>
Cc: psz@...hs.usyd.edu.au, bugtraq@...urityfocus.com
Subject: Re: /proc filesystem allows bypassing directory permissions on
 Linux

On Mon 2009-10-26 13:42:17, Dan Yefimov wrote:
> On 25.10.2009 2:40, psz@...hs.usyd.edu.au wrote:
> >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().
> >
> Paul, in authentic kernels /proc/<PID>/fd/<FD> are symlinks, not
> anything other. There're no such publicly accessible file objects,
> as file descriptors, there're only files (including special ones),
> directories and symlinks. But the above words don't necessary relate
> to patched kernels like distributed by third parties.

Check your facts. Those symlinks are special.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
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