linux-kernel - Re: Posix file capabilities in 2.6.24rc2

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Message-Id: <20071114101251.a1f6214d.chris@friedhoff.org>
Date:	Wed, 14 Nov 2007 10:12:51 +0100
From:	Chris Friedhoff <chris@...edhoff.org>
To:	"Serge E. Hallyn" <sergeh@...ibm.com>
Cc:	"chris@...edhoff.org" <chris@...edhoff.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Posix file capabilities in 2.6.24rc2

Hello Serge,

I wanted only to express what I observed.

A "yes it should" confirms its ok.

And yes, I haven't looked into the patches and the name and commentary
of file-capabilities-clear-fcaps-on-inode-change.patch explains this
already.
I'm preparing to update my page http://www.friedhoff.org/fscaps.html
for 2.6.24, and I also want to explain what one has to take into account
or be beware off. If I stumble about this, I think others will also
(imho).

I have written a script to change suid binaries and servers,
automating the examples I give on the webpage.
In the sequence of commands I was setting fscaps and than chown the
binary. Now with the aforementioned patch the fscaps are removed when
I chown and the script wasn't working anymore. My point is not my
script, it's being surprised and being a bit at a loss. Documenting
this helps to clarify things and users to adopt this feature.

The matter with "xinit:  Operation not permitted..." happens, when I
(unprivileged user) close a from a console started X session. Similar to
Andrew Morton'S http://lkml.org/lkml/2006/11/23/15 . The 2.6.24-rc2
kernel has capabilties enabled but /usr/bin/xinit has no capabilities
set. It remains the black screen with a cursor, the windowmanager is
closed. Is this known? Is this a problem? Does anyone else observes
this?
As far as I understand, I dont have to grant / to use capabilities even
when the kernel has capabilities enabled.

Chris

On Tue, 13 Nov 2007 17:53:18 -0600
"Serge E. Hallyn" <sergeh@...ibm.com> wrote:

> Quoting Chris Friedhoff (chris@...edhoff.org):
> > Hello,
> > 
> > everything works as expected, but ...
> > 
> > closing X and no capabilities set for xinit does shutdown only the
> > windowmanager and not the X server (Xorg server 1.4)
> > Consolemessage is:
> > xinit:  Operation not permitted (errno 1): Can't kill X server
> > 
> > 
> > the xattr capability is removed, when the file is chown'ed.
> 
> Hi Chris,
> 
> yes on chown the capability is removed.  I'm not quite sure what
> you're asking?  Is your setup depending on being able to chown
> while keeping file capabilities?  Can you give some more details?
> 
> thanks,
> -serge

--------------------
Chris Friedhoff
chris@...edhoff.org
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