Remote packet-reception halt via unrecycled XSK buffers

Memory leak in the AF_XDP receive path in Linux allows remote attackers to halt packet reception by filling a zero-copy Rx queue. When __xsk_rcv_zc() cannot publish a descriptor because the receive ring is full, the failure path omits xsk_buff_free(), permanently removing a chunk from the socket's fixed UMEM pool. An AF_XDP application with zero-copy receive processing must already be bound to the targeted interface and queue; sustained inbound traffic can exhaust that queue's pool and stop reception until the application restarts.