linux-kernel - Re: [PATCH] userns/capability: Add user namespace capability

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Message-ID: <CAFLxGvzJONWTbpD8GFfDWDQiPxONrFaRAuXonXXUWaR1pcTUgw@mail.gmail.com>
Date:	Sat, 17 Oct 2015 22:17:36 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Tobias Markus <tobias@...lix.eu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Andrew Morton <akpm@...uxfoundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Christoph Lameter <cl@...ux.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	LSM <linux-security-module@...r.kernel.org>,
	"open list:ABI/API" <linux-api@...r.kernel.org>,
	linux-man <linux-man@...r.kernel.org>
Subject: Re: [PATCH] userns/capability: Add user namespace capability

On Sat, Oct 17, 2015 at 5:58 PM, Tobias Markus <tobias@...lix.eu> wrote:
> One question remains though: Does this break userspace executables that
> expect being able to create user namespaces without priviledge? Since
> creating user namespaces without CAP_SYS_ADMIN was not possible before
> Linux 3.8, programs should already expect a potential EPERM upon calling
> clone. Since creating a user namespace without CAP_SYS_USER_NS would
> also cause EPERM, we should be on the safe side.

In case of doubt, yes it will break existing software.
Hiding user namespaces behind CAP_SYS_USER_NS will not magically
make them secure.

-- 
Thanks,
//richard
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