CVE-2026-23342 bpf: Fix race in cpumap on PREEMPT_RT

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix race in cpumap on PREEMPTRT On PREEMPTRT kernels, the per-CPU xdpbulkqueue bq can be accessed concurrently by multiple preemptible tasks on the same CPU. The original code assumes bqenqueue and cpumapflush run atomically...