netdev - Re: [PATCH v2 02/10] userns: Add per user namespace sysctls.

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Date:	Mon, 25 Jul 2016 19:44:50 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Miller <davem@...emloft.net>
Cc:	containers@...ts.linux-foundation.org, keescook@...omium.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	luto@...capital.net, seth.forshee@...onical.com, kernel@...p.com,
	linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	jann@...jh.net
Subject: Re: [PATCH v2 02/10] userns: Add per user namespace sysctls.

David Miller <davem@...emloft.net> writes:

> From: ebiederm@...ssion.com (Eric W. Biederman)
> Date: Mon, 25 Jul 2016 19:02:01 -0500
>
>>            Which means this change gets has to wait for next cycle.
>
> Ok.

For clarity I intend to merge these changes through the userns tree,
when the issues are resolved.

I Cc'd netdev as there is a limit on the number of network namespaces in
this set which may be of interest to networking folks.

I expect there will be some follow on about adding sanity checking
limits to other kernel data structures like a maximum number of mounts
in a mount namespace, and perhaps a maximum number of routes in a
network namespace.

User namespaces have enabled unprivileged users access to a lot more
data structures and so to catch programs that go crazy we need a lot
more limits.  I believe some of those limits make sense per namespace.
As it is easy in some cases to say any more than Y number of those
per namespace is excessive.   For example a limit of 1,000,000 ipv4
routes per network namespaces is a sanity check as there are
currently 621,649 ipv4 prefixes advertized in bgp.

But that is something to worry about after the merge window.

Eric