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

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Message-Id: <200910270005.n9R05ksw020653@bari.maths.usyd.edu.au>
Date: Tue, 27 Oct 2009 11:05:46 +1100
From: psz@...hs.usyd.edu.au
To: bugtraq@...urityfocus.com, dot@...at.at, pavel@....cz
Subject: Re: /proc filesystem allows bypassing directory permissions on Linux

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

> Attacker opens [directory] and waits. ...
> Attacker uses openat() to open and modify the "private" file.

Surely if the permissions do not allow lookup then openat() will fail.
[The attacker opened directory when it was searcheable; then permissions
were closed; then attacker attempts openat().] Surely directory contents
are not cached??!!

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