CVE-2022-49889 ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters()

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Check for NULL cpubuffer in ringbufferwakewaiters On some machines the number of listed CPUs may be bigger than the actual CPUs that exist. The tracing subsystem allocates a percpu directory with access to the per CP...