linux-kernel - Re: [RFC v1 00/14] Bus1 Kernel Message Bus

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Date:   Wed, 2 Nov 2016 15:45:10 +0100
From:   David Herrmann <dh.herrmann@...il.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, Greg KH <greg@...ah.com>,
        Hannes Reinecke <hare@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Arnd Bergmann <arnd@...db.de>, Tom Gundersen <teg@...m.no>,
        Josh Triplett <josh@...htriplett.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC v1 00/14] Bus1 Kernel Message Bus

Hi

On Thu, Oct 27, 2016 at 2:45 AM, Kirill A. Shutemov
<kirill@...temov.name> wrote:
> On Wed, Oct 26, 2016 at 10:34:30PM +0200, David Herrmann wrote:
>> Long story short: We have uid<->uid quotas so far, which prevent DoS
>> attacks, unless you get access to a ridiculous amount of local UIDs.
>> Details on which resources are accounted can be found in the wiki [1].
>
> Does only root user_ns uid count as separate or per-ns too?
>
> In first case we will have vitually unbounded access to UIDs.
>
> The second case can cap number of user namespaces a user can create while
> using bus1 inside.
>
> Or am I missing something?

We use the exact same mechanism as "struct user_struct" (as defined in
linux/sched.h). One instance corresponds to each kuid_t currently in
use. This is analogous to task, epoll, inotify, fanotify, mqueue,
pipes, keys, ... resource accounting.

Could you elaborate on what problem you see?

Thanks
David