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

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Date:	Tue, 03 Oct 2006 23:07:37 +0400
From:	Stas Sergeev <stsp@...et.ru>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Linux kernel <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Hugh Dickins <hugh@...itas.com>,
	Ulrich Drepper <drepper@...hat.com>, Valdis.Kletnieks@...edu
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

Hi.

Arjan van de Ven wrote:
> then don't put noexec on /dev/shm.
That's obviously possible, but I'd feel safer having
"noexec" on *every* user-writable partition. It used
to work in the past - that way an attacker had no place
to run his binary from.

> ld.so fix is phony. Really; I can always put an "unfixed" ld.so there
> and use it as user. 
See above. In the past it was possible to have "noexec"
on *all* user-writable mounts, so you couldn't run your
own ld.so that easily. Thats why I am reluctant to take
the "if it hurts, just remove noexec" argument.
And since you can run the scripts via binfmt-misc, I'd
also do "chmod 'o-x' perl", so that the direct invocation
of perl to not be possible for unwanted users. Or do not.
At least the approach I propose, allows to do this, so the
"script loader" problem can also be fixed that way.

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