linux-kernel - Re: [PATCH v4] Introduce v3 namespaced file capabilities

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Date:   Tue, 20 Jun 2017 22:56:59 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, xiaolong.ye@...el.com,
        lkp@...org, Vivek Goyal <vgoyal@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>
Subject: Re: [PATCH v4] Introduce v3 namespaced file capabilities

On Tue, Jun 20, 2017 at 8:33 PM, Stefan Berger
<stefanb@...ux.vnet.ibm.com> wrote:
> On 06/20/2017 08:19 AM, Stefan Berger wrote:
>>
>> On 06/20/2017 01:42 AM, Amir Goldstein wrote:

>>>>
>>> Apropos stackable filesystems [cc some overlayfs folks], is there any
>>> way that parts of this work could be generalized towards ns aware
>>> trusted@....* xattr?
>>
>>
>> I am at least removing all string comparison with xattr names from the
>> core code and move the enabled xattr names into a list. For the security.*
>> extended attribute names we would enumerated the enabled ones in that list,
>> only security.capability for now. I am not sure how the trusted.* space
>> works.
>
>
> I extended 'the infrastructure' now to support prefix matching for trusted.*
> and probably others as well. It's fairly easy to do that but would not write
> the code like that for exact string matching to support security.capability.
> The patch lets me write trusted.foo@...=100 from within the userns if
> uid=100 exists, rejects it otherwise. It may be written out as
> trusted.foo@...=1100 for root mapping to uid 1000. I can list this entry on
> the host. For some reason trusted.* is not listed at all inside the userns.
> So something else needs to be enabled as well. For now it looks like this:
>
>
> https://github.com/stefanberger/linux/commit/8ae131e731c9e1def92a2100697632ea35e007d0
>

That looks useful!
I hope someone who knows his way around trusted xattr can say what's missing.

Thanks,
Amir.