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Win guests abort during shutdown on linux host, version 6.18

PostPosted: 10. Apr 2021, 18:45
by HDCompute
A recent upgrade of my Fedora workstation took me to Fedora 32, kernel 5.11 and forced me to upgrade VirtualBox to 6.x, currently 6.18.

Since upgrading VirtualBox from 5.2, I notice my window guests seldom successfully shutdown but usually abort during the shutdown process.

The crash looks to be related to a ShClipboard seg fault as shown in /var/log/messages each time I initiate the shutdown process from inside a Windows guest:

audit[7775]: ANOM_ABEND auid=xxxx uid=xxxx gid=xxx ses=3 subj=kernel pid=xxxx comm="ShClipboard" exe="/usr/lib/virtualbox/VirtualBoxVM" sig=11 res=1
Apr 10 09:22:13 xwing kernel: ShClipboard[7839]: segfault at 20 ip 00007f5d5d68622a sp 00007f5d900bbd40 error 4 in[7f5d5d668000+41000]

Similar segfaults have been observed by others in the forums. As noted by some, the Virtualbox logs do not indicate a problem at the time of the crash.

Note that the segfaults occur even though I have Shared Clipboard disabled in the guest machine settings. Despite my having disabled Shared Clipboard, something is engaging the service during the client's shutdown process. I can also see the service 'clipboard' being started in the log file. There do appear to be problems, but this is at the time of the guest starting up and not the later crash.

00:03:36.035257 VMMDev: Guest Log: Shared Clipboard: New Clipboard API enabled
00:03:36.068140 Shared Clipboard: XQueryExtension failed
00:03:36.068156 Shared Clipboard: Failed to load the XFIXES extension
00:03:36.068160 Shared Clipboard: Initialisation failed: VERR_NOT_SUPPORTED
00:03:36.069630 Shared Clipboard: X11 event thread reported an error while starting
00:03:36.072808 VMMDev: Guest Log: Service 'clipboard' started

Is there some more definite way to turn OFF the shared clipboard service outside of the GUI settings page? Why does it still initialize despite my turning it off in the settings?

I also find that if I do NOT log into the Windows Guest, but initiate Windows shutdown from the Guest's login screen, the ShClipboard segfault does NOT occur. Similarly, if I boot the guest into safe mode, the ShClipboard segfault does NOT occur upon shutdown. I'm assuming that in these cases the Guest Additions are not invoked and somehow that is related to triggering the problems with the shared clipboard service.

I do not know if this is related, but I am running a remote desktop on the HOST machine, so that I am interacting with Virtualbox by way of the x2go remote desktop running LXDE. On my x2go client machine, the clipboard is set to be scrubbed periodically. I've read elsewhere that some people noted problems with the clipboard service when other programs empty it behind VirtualBox's back.

I've attached my log file.

Re: Win guests abort during shutdown on linux host, version 6.18

PostPosted: 21. Apr 2021, 00:28
by HDCompute
I'm still seeing the same abort on shutdown with shclipboard segfaults listed in /var/log/messages for Virtualbox and Guest Additions 6.20.

Is it possible to shut down the shared clipboard service running on the HOST as well as the guests? I've already turned it off for guests, but it's clear that the host is still running the service.

Re: Win guests abort during shutdown on linux host, version 6.18

PostPosted: 9. Jun 2021, 23:22
by HDCompute
This problem still continues with VB/Guest versions 6.22. Everytime, /var/log/messages indicates a segfault in shclipboard, even though the guest has shared clipboard turned off in settings.

I have a bug report submitted, but wondered if anyone else saw these segfaults. In Vitualbox, the guest windows machine never shuts down properly and shows as aborted.

Windows guests without Guest Additions do not exhibit this abort/segfault behavior.

Re: Win guests abort during shutdown on linux host, version 6.18

PostPosted: 18. Jun 2021, 18:08
by HDCompute
I found some indication that this may be a problem with nx-libs in the x2go interface. VirtualBox may be accessing an X API that is not supported by the nx-libs underlying x2go.

As a test, if I run Virtualbox remotely over a ssh-tunneled x-window, the machines shut down without problem. They do not abort like they do under x2go.

Re: Win guests abort during shutdown on linux host, version 6.18

PostPosted: 29. Jul 2021, 00:27
by HDCompute
As of 6.24, so far so good. I have not had a windows client abort during shutdown. I also see no invocation of ShClipboard in /var/log/messages.