So, if you are running a (still supported) Debian Jessie a simple apt-get upgrade isn't gonna cut it:-(
> For the oldstable distribution (jessie), this problem will be fixed in a separate update.
You can check https://security-tracker.debian.org/tracker/CVE-2017-5754 whether the KPTI patch has been released for jessie.
* https://lists.debian.org/debian-security-announce/2018/msg00... (https://news.ycombinator.com/item?id=16076175)
It's not the only operating system where the process is slightly more complex than a kernel update. Windows NT updates require the coöperation of other softwares on one's machine. (-:
I just did the apt-get update; apt-get upgrade dance in a hurry yesterday and thought I might be good. My post was more a reminder to everyone not be lulled into a false sense of security...