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

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Message-Id: <200910262158.n9QLwdLs029586@bari.maths.usyd.edu.au>
Date: Tue, 27 Oct 2009 08:58:39 +1100
From: psz@...hs.usyd.edu.au
To: Casper.Dik@....com, dan@...htwave.net.ru
Cc: bugtraq@...urityfocus.com, matt.bergin@...mail.com, pavel@....cz
Subject: Re: /proc filesystem allows bypassing directory permissions on Linux

Dear Casper and Dan,

> If you can control<pid>, then clearly you have access the file anyway
> simply by controlling it using a debugger.

Sorry, but no. The "attacker" has the file opened O_RDONLY, and cannot
"upgrade" that to O_RDWR.

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