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Date: Mon, 15 Oct 2001 08:11:20 -0400 (EDT)
From: Alexander Viro <viro@math.psu.edu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] "Text file busy" when overwriting libraries
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On Mon, 15 Oct 2001, Alan Cox wrote:

> > Anyone can write it, but what the hell will he do without write access to
> > any place that wouldn't be mounted noexec?  Environment can be restricted
> > even if you give them shell...
> 
> He will type "perl" and interactively issue any damn syscall he likes
> subject to the normal permissions rules. Noexec is only useful for a user
> given virtually nothing.

... and will hit "permission denied" on attempt to exec /usr/bin/perl.
Blanket noexec on /usr instance mounted in his chroot with selective turning
the thing off on some binaries.  And yes, I realize that one can always
hunt for buffer overruns in sh(1)...

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