Kernel panic on boot at dm_crypt

Stefan Unterweger 232.20711 at
Mon Jul 18 01:45:25 PDT 2016

If it helps, I have noticed that the number of -keys- seems to play a
role as well.  The server that won’t boot has two keys configured, the
test machine plays nice enough, but has only one.

‘cryptsetup luksKillSlot’ is enough to trigger the crash—on the ‘real’
server; I haven’t managed to get it to crash on a second machine.  There
may be further interactions with the number of cores, block devices and
their order and whatnot.  I’m still investigating.

As for now, I have removed (via a second machine) all but one key from
the crypto volume, now boot happens more reliably (at first attempt, but
again, that might have been coincidence).

Also, if the crypto device is created (‘luksFormat’) in the same run as
when it is opened (‘luksOpen’), it won’t crash.  If there is a reboot in
between, it usually will.

Adding or not adding encrypted swap at strategic points during this
sequence didn’t change anything. (That was just a hunch.)

I haven‘t seen this problem on a -real- machine, only on virtual ones.
Perhaps some virtio-Bugs show up here as well?


* Sepherosa Ziehau on Thu, Jul 07, 2016 at 03:02:35PM +0800:
> On Thu, Jul 7, 2016 at 2:55 PM, Tomohiro Kusumi <kusumi.tomohiro at> wrote:
> > I've changed SLIST to TAILQ at 3cd1dc08 a while ago, but it seems the
> > location of insertion comes from NetBSD.
> The insertion before the init is highly suspicious, since he got a
> NULL de-reference panic.  However, I don't know why the I/O happens
> simultaneously w/ the init.
> >
> > 2016-07-07 12:16 GMT+09:00 Sepherosa Ziehau <sepherosa at>:
> >>> It looks like a race between the dm init and the I/O path.  i.e. the
> >>> read happens even before the dm init is completed.  Not sure about
> >>> why...

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