Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

um: Add winch to winch_handlers before registering winch IRQ

Registering a winch IRQ is racy, an interrupt may occur before the winch is added to the winch_handlers list.

If that happens, register_winch_irq() adds to that list a winch that is scheduled to be (or has already been) freed, causing a panic later in winch_cleanup().

Avoid the race by adding the winch to the winch_handlers list before registering the IRQ, and rolling back if um_request_irq() fails.