Windows guests abort upon shutdown on linux hosts with segfault indicated in /var/log

[HDCompute]

I have been seeing windows guests crash during shutdown then listing as "aborted" in the main Virtualbox control GUI.

Surveying /var/log/messages indicates segfaults in the shclipboard process.

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 libXt.so.6.0.0[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. Shared Clipboard is DISABLED for the guests. I do not make use of this feature and so turn it off for my guest machines.

Host: Fedora 32 Linux running kernel 5.11 Virtualbox installation via virtualbox.org site: Fedora repo and manually downloaded extension pack.

I've noticed the problem since upgrading from Virtualbox 5.2 to Virtualbox 6.x as part of an upgrade from Fedora 30 to Fedora 32 several months ago.

The problem has persisted through a recent upgrade to Virtualbox 6.20.

If I do not log into the Guest after booting the guest, but shut it down from the Guest login screen, the guest shuts down without crashing. I'm assuming that this is related to engaging some part of the Guest additions services after logging into the guest. Again, Shared Clipboard has been turned off in the guest's options within the Virtualbox control GUI.

As I understand it, the shared clipboard will run services on both the host and the guest to manage the data exchange. It appears that something may trigger a poling of the clipboard from the host side during guest shutdown, independent of whether the service is running on the guest.

[HDCompute]

Virtualbox log file captured at the time of the crash.

[HDCompute]

Owing to the pandemic, I am running these virtual windows guests on the host Fedora machine through a remote desktop connection to the host using x2go. I have not had an opportunity to test whether this crash occurs directly at the host console.

[HDCompute]

Update: Still seeing these segfault aborts with 6.1.22. No indication in the log. Segfault errors in /var/log/messages for ShClipboard.

Replying to HDCompute:

Owing to the pandemic, I am running these virtual windows guests on the host Fedora machine through a remote desktop connection to the host using x2go. I have not had an opportunity to test whether this crash occurs directly at the host console.

[HDCompute]

I have several guest machines without the guest additions that do NOT have this problem. Also, uninstalling the guest additions from the host (while in safe mode) eliminates the problem.

Something about the guest additions within the windows host interacts with the host's shclipboard service even when clipboard is turned off in settings.

[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.

​https://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=581

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.

[HDCompute]

As of Virtualbox 6.1.24, I am not seeing ShClipboard/segfaults when I shut down my windows guests run remotely over an x2go session.

Virtualbox 6.1.24 x2goserver 4.1.0.3 x2go client: 4.1.2.2