[Pkg-utopia-maintainers] Bug#914948: udisks2: udisksctl power-off causes system freeze

[EP]

Package: udisks2
Version: 2.1.8-1
Severity: important

Dear Maintainer,

on my system with Samsung 970 Evo M2 SSD, the command udisksctl
"power-off --block-device /dev/sdx" causes a complete system freeze.
Input devices are not responding, only hard reset is possible.
Logfiles report series of null bytes only (syslog, messages, even
jounalctl -f).
The problem occurred after installing a new system on a M2 SSD. The
problem does not occur using my old (quite similar) system, installed on
a SATA SSD (Samsung 850 Pro).
It does not depend on which kind of USB device (HDD or pendrives) is
powered off.
The power-off is successful before the system freezes. (though nothing
is recorded in logfiles)
The only way to avoid the freeze is not using the command (and the
thunar filmanager unmount feature using it).
It may be a hardware problem, but other users have similar problems.

My hardware (unchanged except SSD):
ASRock Z170 Extreme4 (latest firmware)
Intel i5 6600T (using integrated graphics)
8 GB RAM 


-- System Information:
Debian Release: 9.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-8-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_AT.utf8, LC_CTYPE=de_AT.utf8 (charmap=UTF-8),
LANGUAGE=de_AT:de (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages udisks2 depends on:
ii  dbus                   1.10.26-0+deb9u1
ii  libacl1                2.2.52-3+b1
ii  libatasmart4           0.19-4+b1
ii  libc6                  2.24-11+deb9u3
ii  libglib2.0-0           2.50.3-2
ii  libgudev-1.0-0         230-3
ii  libpam-systemd         232-25+deb9u6
ii  libpolkit-agent-1-0    0.105-18
ii  libpolkit-gobject-1-0  0.105-18
ii  libsystemd0            232-25+deb9u6
ii  libudisks2-0           2.1.8-1
ii  parted                 3.2-17
ii  udev                   232-25+deb9u6

Versions of packages udisks2 recommends:
ii  dosfstools   4.1-1
ii  eject        2.1.5+deb1+cvs20081104-13.2
ii  exfat-utils  1.2.5-2
ii  gdisk        1.0.1-1
ii  ntfs-3g      1:2016.2.22AR.1+dfsg-1
ii  policykit-1  0.105-18

Versions of packages udisks2 suggests:
pn  btrfs-progs | btrfs-tools  <none>
pn  cryptsetup-bin             <none>
pn  mdadm                      <none>
pn  reiserfsprogs              <none>
pn  xfsprogs                   <none>

-- no debconf information