/usr/sbin/libvirtd:11:virSecurityManagerTransactionStart:qemuSecurityRestoreAllLabel:qemuProcessStop:qemuDomainSaveInternal:qemuDomainManagedSave

[errors.ubuntu.com bug bridge]

The Ubuntu Error Tracker has been receiving reports about a problem regarding libvirt. This problem was most recently seen with package version 6.0.0-0ubuntu8.12, the problem page at https://errors.ubuntu.com/problem/227a7f4d7b698c340f928038ad78fcaf4bb2de5a contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

Also another slightly different trace seems to be the same
https://errors.ubuntu.com/problem/49e76f2070b85b5bb1ef09b837c90f9b2fb8bf47

[Christian Ehrhardt  (paelzer)]

The crash is in
   255 int
   256 virSecurityManagerTransactionStart(virSecurityManagerPtr mgr)
   257 {
   258 int ret = 0;
   259
   260 virObjectLock(mgr);
   261 if (mgr->drv->transactionStart)
   262 ret = mgr->drv->transactionStart(mgr);
   263 virObjectUnlock(mgr);
   264 return ret;
   265 }

virObjectLock checks references before access.
But one can think of "mgr->drv" being a bad pointer and then the mgr->drv->transactionStart being the crash.

[Christian Ehrhardt  (paelzer)]

It still looks the same in recent master.

[Christian Ehrhardt  (paelzer)]

Reported for an upstream discussion
https://gitlab.com/libvirt/libvirt/-/issues/200

[Christian Ehrhardt  (paelzer)]

Fixed in 6.6 and later, but nobody is sure via which changes exactly - therefore we can't backport anything yet.