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From: David Herrmann <dh.herrmann@gmail.com>
Date: Wed, 2 Nov 2016 15:45:10 +0100
Message-ID: <CANq1E4QR9ksj_h-+C-P1NuHqRaLZaHU=w8LDaUPdAZo0gG4C2A@mail.gmail.com>
Subject: Re: [RFC v1 00/14] Bus1 Kernel Message Bus
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@amacapital.net>, Jiri Kosina <jikos@kernel.org>,
        Greg KH <greg@kroah.com>, Hannes Reinecke <hare@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>, Arnd Bergmann <arnd@arndb.de>,
        Tom Gundersen <teg@jklm.no>, Josh Triplett <josh@joshtriplett.org>,
        Andrew Morton <akpm@linux-foundation.org>
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Hi

On Thu, Oct 27, 2016 at 2:45 AM, Kirill A. Shutemov
<kirill@shutemov.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