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

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Date:	Thu, 28 Sep 2006 00:33:50 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Stas Sergeev <stsp@...et.ru>
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

On Tue, 2006-09-26 at 23:46 +0400, Stas Sergeev wrote:
> Hi Guys.
> 
> Noone provided a reason for (or even tried to defend)
> the fact that PROT_EXEC is rejected by "noexec" even
> for MAP_PRIVATE, while, say, PROT_WRITE is *not* rejected
> for "ro" filesystem for MAP_PRIVATE. What was argued is
> only MAP_SHARED.

is it?

> - The programs (like AFAIK wine) use MAP_PRIVATE mmaps to
> access the windows dlls, which are usually on a "noexec"
> fat or ntfs partitions. Wine might be smart enough not to
> break but fallback to read(), but this is slower and more
> memory-consuming. Some other program may not be that smart
> and break. So there is clearly a need for MAP_PRIVATE with
> PROT_EXEC on the noexec partitions.

but really again you are degrading what noexec means.
It now starts to mean "only don't execute a little bit" rather than
"deny execute requests"....


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