Message-ID: <45175C7B.7040005@aknet.ru>
Date: Mon, 25 Sep 2006 08:35:07 +0400
From: Stas Sergeev <stsp@aknet.ru>
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To: Valdis.Kletnieks@vt.edu
Cc: Ulrich Drepper <drepper@redhat.com>, Hugh Dickins <hugh@veritas.com>,
       Andrew Morton <akpm@osdl.org>,
       Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps
References: <45150CD7.4010708@aknet.ru> <Pine.LNX.4.64.0609231555390.27012@blonde.wat.veritas.com> <45155499.4000209@redhat.com>            <45155707.4010906@aknet.ru> <200609250112.k8P1CTfZ019880@turing-police.cc.vt.edu>
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Hi.

Valdis.Kletnieks@vt.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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