linux-kernel - Re: [PATCH 2/2] user_namespaces.7: Update the documention to reflect the fixes for negative groups

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Date:	Thu, 12 Feb 2015 11:11:09 +0100
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	mtk.manpages@...il.com,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Josh Triplett <josh@...htriplett.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	linux-man <linux-man@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	Casey Schaufler <casey@...aufler-ca.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Richard Weinberger <richard@....at>,
	Kenton Varda <kenton@...dstorm.io>,
	stable <stable@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 2/2] user_namespaces.7: Update the documention to reflect
 the fixes for negative groups

On 02/11/2015 03:01 PM, Eric W. Biederman wrote:
> "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com> writes:
> 
>> Hi Eric,
>>
>> Ping!
>>
>> Cheers,
>>
>> Michael
>>
>>
>> On 2 February 2015 at 16:37, Michael Kerrisk (man-pages)
>> <mtk.manpages@...il.com> wrote:
>>> Hi Eric,
>>>
>>> Thanks for writing this up!
>>>
>>> On 12/12/2014 10:54 PM, Eric W. Biederman wrote:
>>>>
>>>> Files with access permissions such as ---rwx---rwx give fewer
>>>> permissions to their group then they do to everyone else.  Which means
>>>> dropping groups with setgroups(0, NULL) actually grants a process
>>>> privileges.
>>>>
>>>> The uprivileged setting of gid_map turned out not to be safe after
>         ^^^^^^^^^^^
> unprivileged  -- typo fix

Thanks for confirming.

>>>> this change.  Privilege setting of gid_map can be interpreted as
>>>> meaning yes it is ok to drop groups.
>>>
>>> I had trouble to parse that sentence (and I'd like to make sure that
>>> the right sentence ends up in the commit message). Did you mean:
>>>
>>>     "*Unprivileged* setting of gid_map can be interpreted as meaning
>>>      yes it is ok to drop groups"
>>> ?
>>>
>>> Or something else?
> 
> 
> I meant:  Setting of gid_map with privilege has been clarified to mean
> that dropping groups is ok.  This allows existing programs that set
> gid_map with privilege to work without changes.  That is newgidmap
> continues to work unchanged.

Thanks. I added that text to the changelog message.

Cheers,

Michael



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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