linux-kernel - Re: [PATCH] Make core_pattern support namespace

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Message-ID: <87k2m33xgj.fsf@x220.int.ebiederm.org>
Date:	Wed, 17 Feb 2016 14:15:24 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Mateusz Guzik <mguzik@...hat.com>
Cc:	Zhao Lei <zhaolei@...fujitsu.com>,
	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make core_pattern support namespace

Mateusz Guzik <mguzik@...hat.com> writes:

> On Tue, Feb 16, 2016 at 07:33:39PM +0800, Zhao Lei wrote:
>> Currently, each container shared one copy of coredump setting
>> with the host system, if host system changed the setting, each
>> running containers will be affected.
>> 
>> Moreover, it is not easy to let each container keeping their own
>> coredump setting.
>> 
>> We can use some workaround as pipe program to make the second
>> requirement possible, but it is not simple, and both host and
>> container are limited to set to fixed pipe program.
>> In one word, for host running contailer, we can't change core_pattern
>> anymore.
>> To make the problem more hard, if a host running more than one
>> container product, each product will try to snatch the global
>> coredump setting to fit their own requirement.
>> 
>> For container based on namespace design, it is good to allow
>> each container keeping their own coredump setting.
>> 
>> It will bring us following benefit:
>> 1: Each container can change their own coredump setting
>>    based on operation on /proc/sys/kernel/core_pattern
>> 2: Coredump setting changed in host will not affect
>>    running containers.
>> 3: Support both case of "putting coredump in guest" and
>>    "putting curedump in host".
>> 
>> Each namespace-based software(lxc, docker, ..) can use this function
>> to custom their dump setting.
>> 
>> And this function makes each continer working as separate system,
>> it fit for design goal of namespace.
>> 
>
> Sorry if this is a false alarm, I don't have easy means to test it, but
> is not this an immediate privilege escalation?

It is.  This is why we do not currently have a per namespace setting.

Solving the user mode helper problem is technically a fair amount of
work, if not theoretically challenging.

Eric