In the Linux kernel, the following vulnerability has been resolved:
xen/evtchn: avoid WARN() when unbinding an event channel
When unbinding a user event channel, the related handler might be called a last time in case the kernel was built with CONFIGDEBUGSHIRQ. This might cause a WARN() in the handler.
Avoid that by adding an "unbinding" flag to struct user_event which will short circuit the handler.