Kernel panic on 5.3.1-arch1-1-ARCH

[Jason A. Donenfeld]

This isn't WireGuard, actually. It's a line in wg-quick's bash that
says `ip rule add ... suppress_prefix ...`.

You can reproduce the kernel crash without WireGuard anywhere in the
equation with this sequence:

ip netns add crash
ip -n crash link add dummy1 type dummy
ip -n crash link set dummy1 up
ip -n crash -6 route add default dev dummy1
ip -n crash -6 rule add table main suppress_prefixlength 0
ip netns exec crash ping -f -c 1000 -W 1 1234::1 || true
ip -n crash -6 rule del table main suppress_prefixlength 0
ip -n crash link del dummy1
ip netns del crash

I submitted a patch for this upstream here:

https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=ca7a03c4175366a92cee0ccc4fec0038c3266e26

It's been backported to stable already. Update your kernel to 5.3.4
and things should work again for you.

Jason