CVE-2024-39292 um: Add winch to winch_handlers before registering winch IRQ

In the Linux kernel, the following vulnerability has been resolved: um: Add winch to winchhandlers before registering winch IRQ Registering a winch IRQ is racy, an interrupt may occur before the winch is added to the winchhandlers list. If that happens, registerwinchirq adds to that list a winch...