Re: [RESEND RFC PATCH 0/1] CAP_SYS_NICE inside user namespace

From: Prakash Sangappa <prakash.sangappa@oracle.com>
To: Jann Horn <jannh@google.com>
Cc: kernel list <linux-kernel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Christian Brauner <christian@brauner.io>
Subject: Re: [RESEND RFC PATCH 0/1] CAP_SYS_NICE inside user namespace
Date: Mon, 18 Nov 2019 12:34:45 -0800	[thread overview]
Message-ID: <9a63f7ae-562e-67a6-8f40-050c58c08933@oracle.com> (raw)
In-Reply-To: <CAG48ez3HfUx2aRvqR_bWnGoTshrHnUzxUNt7K6Sv7cqtPDWaWw@mail.gmail.com>

On 11/18/19 11:36 AM, Jann Horn wrote:
> On Mon, Nov 18, 2019 at 6:04 PM Prakash Sangappa
> <prakash.sangappa@oracle.com> wrote:
>> Some of the capabilities(7) which affect system wide resources, are ineffective
>> inside user namespaces. This restriction applies even to root user( uid 0)
>> from init namespace mapped into the user namespace. One such capability
>> is CAP_SYS_NICE which is required to change process priority. As a result of
>> which the root user cannot perform operations like increase a process priority
>> using -ve nice value or set RT priority on processes inside the user namespace.
>> A workaround to deal with this restriction is to use the help of a process /
>> daemon running outside the user namespace to change process priority, which is
>> a an inconvenience.
> What is the goal here, in the big picture? Is your goal to allow
> container admins to control the priorities of their tasks *relative to
> each other*, or do you actually explicitly want container A to be able
> to decide that its current workload is more timing-sensitive than
> container B's?

It is more the latter. Admin should be able to explicitly decide that 
container A
workload is to be given priority over other containers.