Merge branch 'netns-sysctl-isolation'

Jonathon Reinhart says:

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Ensuring net sysctl isolation

This patchset is the result of an audit of /proc/sys/net to prove that
it is safe to be mouted read-write in a container when a net namespace
is in use. See [1].

The first commit adds code to detect sysctls which are not netns-safe,
and can "leak" changes to other net namespaces.

My manual audit found, and the above feature confirmed, that there are
two nf_conntrack sysctls which are in fact not netns-safe.

I considered sending the latter to netfilter-devel, but I think it's
better to have both together on net-next: Adding only the former causes
undesirable warnings in the kernel log.

[1]: https://github.com/opencontainers/runc/issues/2826


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Signed-off-by: David S. Miller <davem@davemloft.net>