linux-kernel - Re: [PATCH 4/7] allow killing tasks in your own or child userns

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Message-ID: <20110110232335.GA27029@wavehammer.waldi.eu.org>
Date:	Tue, 11 Jan 2011 00:23:35 +0100
From:	Bastian Blank <bastian@...di.eu.org>
To:	Serge Hallyn <serge.hallyn@...onical.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <kees.cook@...onical.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH 4/7] allow killing tasks in your own or child userns

On Mon, Jan 10, 2011 at 04:51:51PM -0600, Serge Hallyn wrote:
> Quoting Bastian Blank (bastian@...di.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.

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.

Bastian

-- 
Bones: "The man's DEAD, Jim!"
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