qemu -- denial of service vulnerability in USB EHCI emulation support

Prasad J Pandit, Red Hat Product Security Team, reports:

Qemu emulator built with the USB EHCI emulation support is
vulnerable to an infinite loop issue. It occurs during communication
between host controller interface(EHCI) and a respective device
driver. These two communicate via a isochronous transfer descriptor
list(iTD) and an infinite loop unfolds if there is a closed loop in
this list.
A privileges user inside guest could use this flaw to consume
excessive CPU cycles & resources on the host.