perf_event_uncore doesn't consider capabilities

[voidbert]

The perf_event_uncore component checks if the user has permissions for reading uncore counters before trying to do so. It does so by running the this code, abridged below:

// read /proc/sys/kernel/perf_event_paranoid
// ...

if ((paranoid_level>0) && (getuid()!=0)) {
    // fail due to lack of permissions
}

// Success

However, checking for root is too strong of a check, as it's possible for a regular user to be able to read counters even with perf_event_paranoid > 0. To achieve that, the current thread must have one of the following capabilities: CAP_SYS_ADMIN or CAP_PERFMON.