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

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Date:	Wed, 04 Oct 2006 23:48:46 +0400
From:	Stas Sergeev <stsp@...et.ru>
To:	Jesper Juhl <jesper.juhl@...il.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	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.

Jesper Juhl wrote:
> So first you mount /dev/shm with 'noexec', thereby telling the system
> "please make shared memory non executable".
Well, what do I want to tell to the system when
mounting /dev/shm with "noexec" is a difficult
point to discuss. In my opinion (and it was so
for ages) I only tell it to not execute the
binaries from there. In your opinion I am saying
to make the shared memory not executable, but on
the other hand I am just mmaping some file, and
mmaping a file with PROT_EXEC never required an
exec perm for that file, so I wonder why "noexec"
is different here.
But as I said, this is a bit difficult to discuss,
so I was trying to avoid touching MAP_SHARED for now.
Please tell me how your logic applies to MAP_PRIVATE
instead, which is affected the same way. (considering
mprotect, MAP_ANONYMOUS then read(), "ro" not denying
PROT_WRITE, etc)

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