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From: "Eric W.Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Subject: Re: [CFT][PATCH 7/8] userns: Add a knob to disable setgroups on a per
	user namespace basis
Date: Tue, 09 Dec 2014 18:04:17 -0600
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On December 9, 2014 4:28:38 PM CST, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> wrote:
>On Tue, Dec 9, 2014 at 12:42 PM, Eric W. Biederman
><ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> 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-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
>
>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.

Eric