linux-kernel - Re: [patch] remove MNT_NOEXEC check for PROT

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Date:	Sun, 24 Sep 2006 20:59:38 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Stas Sergeev <stsp@...et.ru>
Cc:	Ulrich Drepper <drepper@...hat.com>,
	Hugh Dickins <hugh@...itas.com>, Andrew Morton <akpm@...l.org>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

Ar Sul, 2006-09-24 am 20:31 +0400, ysgrifennodd Stas Sergeev:
> 1. mprotect() the existing mapping to PROT_EXEC and bypass the
> checks (but you can easily restrict that by patching mprotect()).

Bug: To be fixed

> 2. Do the anonymous mmap with PROT_EXEC set, then simply read()
> the code there, then execute. This you *can not* restrict!

Its a non-finite turing machine, you can also execute an interpreter.

> Now, the breakage of the properly-written programs forces people
> to stop using "noexec" on /dev/shm-mounted tmpfs. As far as I

But you've already just argued that this isn't useful anyway ?

> understand, having the single writeable and executable mountpoint
> is almost as bad as having all of them. The attacker will now simply
> put his binary into /dev/shm.

SELinux

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