linux-kernel - Re: O_NOLINK for open()

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Message-ID: <jetzpza7ci.fsf@sykes.suse.de>
Date:	Wed, 12 Sep 2007 23:42:37 +0200
From:	Andreas Schwab <schwab@...e.de>
To:	Brent Casavant <bcasavan@....com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: O_NOLINK for open()

Brent Casavant <bcasavan@....com> writes:

> I could mmap a temporary tmpfs file (tmpfs so that if there is a
> machine crash no sensitive data persists) which is created with
> permissions of 0, immediately unlink it, and pass the file
> descriptor through an AF_UNIX socket.  This does open up a very
> small window of vulnerability if another process is able to chmod
> the file and open it before the unlink.

Only the owner can chmod a file, so why is that a vulnerability?

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."
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