Bug#839607: Robustify manager_dispatch_notify_fd()

[Florian Weimer]

* Salvatore Bonaccorso:

> There were two CVE assingments for systemd recently, CVE-2016-7795 and
> CVE-2016-7796, and assigned here:
> https://marc.info/?l=oss-security&m=147521835218986&w=2
>
> CVE-2016-7795 is for
>
> https://github.com/systemd/systemd/issues/4234
> https://www.agwa.name/blog/post/how_to_crash_systemd_in_one_tweet
>
> which does not affect stable.
>
> CVE-2016-7796 is for
>
> https://github.com/systemd/systemd/issues/4234#issuecomment-250441246
> with fix https://github.com/systemd/systemd/pull/4240 which is this
> bug #839607.
>
> Does this look correct to you as well, Florian?

Based on <https://marc.info/?l=oss-security&m=147521835218986&w=2>,
I agree.