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Date: Sat, 2 Nov 2002 19:35:25 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Alexander Viro <viro@math.psu.edu>
cc: Olaf Dietsche <olaf.dietsche#list.linux-kernel@t-online.de>,
       "Theodore Ts'o" <tytso@mit.edu>, Dax Kelson <dax@gurulabs.com>,
       Rusty Russell <rusty@rustcorp.com.au>, <linux-kernel@vger.kernel.org>,
       <davej@suse.de>
Subject: Re: Filesystem Capabilities in 2.6?
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On Sat, 2 Nov 2002, Linus Torvalds wrote:

> 
> On Sat, 2 Nov 2002, Alexander Viro wrote:
> >
> > 	<shrug> that can be done without doing anything to filesystem.
> > Namely, turn current "nosuid" of vfsmount into a mask of capabilities.
> > Then use bindings instead of links.
> 
> I like that idea. It's very explicit, and clearly name-based, and we do
> have 99% of the support for it already.

It occurs to me that we actually do have the "extended symlink" concept in
UNIX already: the existing "#!" escape for executables is really exactly
that. It's just a structured symlink, except the extension is not a
capability, but rather it's the script to be fed to the executable.

With a simple extended binfmt_misc.c or binfmt_script.c, we could do a
capability escape (that only removes capabilities, but allows for suid
shells) fairly easily if people really want it. And it would work on any
almost-UNIXy filesystem, including NFS etc.

But I like Al's idea of mount binds even more, although it requires maybe
a bit more administration.

		Linus

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