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

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Date:	Sun, 24 Sep 2006 02:53:38 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Stas Sergeev <stsp@...et.ru>
Cc:	Andrew Morton <akpm@...l.org>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

On Sat, 2006-09-23 at 14:30 +0400, Stas Sergeev wrote:
> Hi Andrew.
> 
> I am not sure at all whether this patch is appreciated
> or not. The on-list query yielded no results, but I have
> to try. :)
> 
> This patch removes the MNT_NOEXEC check for the PROT_EXEC
> mappings. 

so you remove a security check ...

> That allows to mount tmpfs with "noexec" option
> without breaking the existing apps, which is what debian
> wants to do for sequrity reasons:
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=386945

... to add a "security" feature?

sounds like the wrong tradeoff!

If you can mmap PROT_EXEC the "noexec" mount option doesn't mean
anything! Because a elf binary loader is easily written in
perl/shell/whatever, the kernel "x" bit is just a convenience there!
The PROT_EXEC check at least makes it a bit harder to do anything like
this; not impossible obviously

Greetings,
   Arjan van de Ven

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