Backport: "net: Make tcp_allowed_congestion_control readonly in non-init netns"

Hello,

Please apply upstream git commit 2671fa4dc010 ("netfilter: conntrack:
Make global sysctls readonly in non-init netns") to the stable trees.

BTW netdev-FAQ.txt said not to send networking patches to stable, but
Greg suggested I do it this way :-)

On Mon, Apr 19, 2021 at 8:04 AM Greg KH [off-list ref] wrote:

For something like this, how about just waiting until it hits Linus's
tree and then email stable@vger.kernel.org saying, "please apply git
commit <SHA1> to the stable trees." and we can do so then.

If there's a better way I should go about this, please let me know!

Thanks,
Jonathon Reinhart