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Date: Fri, 5 Oct 2001 10:44:21 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Horst von Brand <vonbrand@inf.utfsm.cl>
cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Alexander Viro <viro@math.psu.edu>, <linux-kernel@vger.kernel.org>
Subject: Re: Security question: "Text file busy" overwriting executables but
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On Fri, 5 Oct 2001, Horst von Brand wrote:

> Linus Torvalds <torvalds@transmeta.com> said:
> > On 5 Oct 2001, Eric W. Biederman wrote:
>
> [...]
>
> > > Currently checking to see if the file is executable looks good
> > > enough.
> >
> > [ executable by the user in question, not just anybody ]
> >
> > Yes, I suspect it is.
>
> Who is "user in question"? It is quite legal (if strange) to have a file
> user A can modify, but not execute, while B can execute it.

The "user in question" being the one that actually does the
mmap(MAP_DENYWRITE). If _he_ can execute the file, that would be
reason enough to think that he can deny others from writing to it while he
has it mapped..

		Linus

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