CVE-2021-47574

In the Linux kernel, the following vulnerability has been resolved: xen/netfront: harden netfront against event channel storms The Xen netfront driver is still vulnerable for an attack via excessive number of events sent by the backend. Fix that by using lateeoi event channels. For being able to detect the case of no rx responses being added while the carrier is down a new lock is needed in order to update and test rsp_cons and the number of seen unconsumed responses atomically. This is part of XSA-391 --- V2: - don't eoi irq in case of interface set broken (Jan Beulich) - handle carrier off + no new responses added (Jan Beulich) V3: - add rx_ prefix to rsp_unconsumed (Jan Beulich) - correct xennet_set_rx_rsp_cons() spelling (Jan Beulich)