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

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Date:	Mon, 25 Sep 2006 08:35:07 +0400
From:	Stas Sergeev <stsp@...et.ru>
To:	Valdis.Kletnieks@...edu
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

Hi.

Valdis.Kletnieks@...edu wrote:
>> But why exactly? They do:
>> shm_open();
>> mmap(PROT_READ|PROT_WRITE|PROT_EXEC);
>> and mmap fails.
>> Where is the fault of an app here?
> Are you suggesting that it's not an app's fault/problem if it tries to
> open a writable file on a R/O filesystem?  Because it's essentially the
> same problem....
It is not really the same - the app is not trying to
create an "executable" file on a noexec filesystem.
PROT_EXEC never required the exec permission on a file
btw. The MAP_PRIVATE mmap roughly means a read of the
file into the memory, where the program can do anything
with its data, including an execution. Does the R/O
filesystem disallow PROT_WRITE for MAP_PRIVATE? Haven't
tried, but I hope it doesn't.

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