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Date: Mon, 15 Oct 2001 13:24:59 +0200
From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: Aaron Lehmann <aaronl@vitelus.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>, linux-kernel@vger.kernel.org
Subject: Re: Security question: "Text file busy" overwriting executables but not shared libraries?
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Aaron Lehmann wrote:
> > > But it does have the advantage of allowing the sharing of memory, does
> > > it not?
> > 
> > Only if you are going to write to the data.
> 
> Why? If gcc and another application read the source file with an
> mmap() with the right parameters (read-only), it would only be shared
> between them, as I understand it. If they both read() the file into
> private buffers those can not be shared.

And furthermore, the private buffers cannot be shared with the
filesystem's page cache.

-- Jamie

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