linux-kernel - Re: [CFT][PATCH 7/8] userns: Add a knob to disable setgroups on a per user namespace basis

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Date:	Tue, 9 Dec 2014 16:21:23 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	"Eric W.Biederman" <ebiederm@...ssion.com>
Cc:	Linux Containers <containers@...ts.linux-foundation.org>,
	Josh Triplett <josh@...htriplett.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	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>
Subject: Re: [CFT][PATCH 7/8] userns: Add a knob to disable setgroups on a per
 user namespace basis

On Tue, Dec 9, 2014 at 4:04 PM, Eric W.Biederman <ebiederm@...ssion.com> wrote:
>
>
> On December 9, 2014 4:28:38 PM CST, Andy Lutomirski <luto@...capital.net> wrote:
>>On Tue, Dec 9, 2014 at 12:42 PM, Eric W. Biederman
>><ebiederm@...ssion.com> wrote:
>>>
>>> - Expose the knob to user space through a proc file
>>/proc/<pid>/setgroups
>>>
>>>   A value of "deny" means the setgroups system call is disabled in
>>the
>>>   current processes user namespace and can not be enabled in the
>>>   future in this user namespace.
>>>
>>>   A value of "allow" means the segtoups system call is enabled.
>>>
>>> - Descendant user namespaces inherit the value of setgroups from
>>>   their parents.
>>>
>>> - A proc file is used (instead of a sysctl) as sysctls
>>>   currently do not pass in a struct file so file_ns_capable
>>>   is unusable.
>>
>>Reviewed-by: Andy Lutomirski <luto@...capital.net>
>>
>>But I still don't like the name "setgroups".  People may look at that
>>and have no clue what the scope of the setting is.  And anyone who, as
>>root, writes "deny" to /proc/self/setgroups, thinking that it acts on
>>self, will be in for a surprise.
>
> True setgroups isn't perfect.  Documenting it in a manpage may have to be enough. The only real improvement I can think of would be to make the setting a sysctl.   But I think pursuing that approaches the point where perfection is the enemy of getting this problem fixed.
>

Would "userns_setgroups" be okay?

--Andy

> Eric



-- 
Andy Lutomirski
AMA Capital Management, LLC
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