qemu -- denial of service vulnerability in Rocker switch emulation

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

Qemu emulator built with the Rocker switch emulation support is
vulnerable to an off-by-one error. It happens while processing
transmit(tx) descriptors in ‘tx_consume’ routine, if a descriptor
was to have more than allowed (ROCKER_TX_FRAGS_MAX=16) fragments.

A privileged user inside guest could use this flaw to cause memory
leakage on the host or crash the Qemu process instance resulting in
DoS issue.