Ubuntu
systemd package

  1. Bug #1795921
  2. Comment #12

Comment 12 for bug 1795921

Revision history for this message
Zbigniew Jędrzejewski-Szmek (zbyszek-in) wrote : Re: [Bug 1795921] Re: Out-of-Bounds write in systemd-networkd dhcpv6 option handling

On Tue, Oct 30, 2018 at 08:16:27PM -0000, Clemens Fuchslocher wrote:
> Are there any workarounds for Ubuntu 16.04?
>
> Can I set /proc/sys/net/ipv6/conf/all/accept_ra to 0 to ignore the
> Router Advertisements?

There are two settings: the accept_ra sysctl in the kernel, and
IPv6AcceptRa= in systemd. The second setting can override the kernel
setting, but it defaults to "use the kernel default". The kernel
defaults to "enabled if local forwarding is disabled".
So accept_ra=0 is honoured as long as IPv6AcceptRa= is *not* set to true.

But the code where the error is is in the dhcpv6 client part. It can
be triggered in two different ways: upon reception of a RA, or explicitly
by using DHCP=yes or DHCP=ipv6. So both settings (accept_ra=/IPv6AcceptRa=
and DHCP=) have to be set to 0/no to mitigate the issue.
(Note though DHCP=no is the default.)

This is my understanding, but I'm not too familiar with this code, so
it'd be great if somebody could confirm.

Zbyszek