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Date: Tue, 11 Jan 2011 01:31:52 +0000
From: "Serge E. Hallyn" <serge@hallyn.com>
To: Bastian Blank <bastian@waldi.eu.org>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        containers@lists.linux-foundation.org,
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        "Eric W. Biederman" <ebiederm@xmission.com>,
        Kees Cook <kees.cook@canonical.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [PATCH 4/7] allow killing tasks in your own or child userns
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Quoting Bastian Blank (bastian@waldi.eu.org):
> On Mon, Jan 10, 2011 at 04:51:51PM -0600, Serge Hallyn wrote:
> > Quoting Bastian Blank (bastian@waldi.eu.org):
> > > Isn't that equal to this?
> > > 
> > > 	if (ns_capable(tcred->user->user_ns, CAP_KILL))
> > > 		return 1;
> > > 
> > > 	if (cred->user->user_ns == tcred->user->user_ns &&
> > > 	    (cred->euid == tcred->suid ||
> > > 	     cred->euid == tcred->uid ||
> > > 	     cred->uid == tcred->suid ||
> > > 	     cred->uid == tcred->uid))
> > > 		return 1;
> > > 
> > > 	return 0;
> > > 
> > > I would consider this much easier to read.
> > 
> > Unfortunately, it's actually not equivalent.  when capable()
> > returns success, then it sets the current->flags |= PF_SUPERPRIV.
> > If permission is granted based on userids and the capability
> > isn't needed, then we don't want to needlessly set PF_SUPERPRIV.
> 
> Well, then switch the two if-clauses.

hup, will do, much nicer, thanks.

> What is this flag used for anyway? I only see it used in the accounting
> stuff, and if every user can get it, it is not longer useful.

hm, I'm not sure...  maybe noone is using it!