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[Possibly fake news] [DNG] Linux system can be brought down by sending SIGILL to Systemd




On Fri, May 24, 2019 at 02:01:35PM -0700, Fred wrote:
> Hello,
> I subscribe to the Devuan Linux mailing list.  This posting just
> arrived and it appears quite important to Debian.

[about sending SIGILL to systemd]

This is most probably fake news.

You have to have appropriate permissions to send *any* signal to a
proces. From the kill(2) man page

  "For a process to have permission to send a signal, it
  must either be privileged (under Linux: have the  CAP_KILL
  capability  in the  user namespace  of  the  target process),
  or the real or effective user ID of the sending process must
  equal the real or saved set-user-ID of the target process.
  In the case of SIGCONT, it suffices when the sending and
  receiving processes belong to the same session.  (Historically,
  the rules were different; see NOTES.)"

That means that to send SIGILL to pid 1 you most probably gotta be
root (systemd or not). And then, there are more classy ways to bring
your system down anyway.

Folks, please double-check that stuff before reposting. I don't want
the Debian mailing list to become Fakebook or Twitter.

Cheers
-- tomás

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