On Tue, Jan 31, 2017 at 11:27:10AM +0100, Peter Zijlstra wrote: > Subject: perf: Fix crash in perf_event_read() > > Alexei had his box explode because doing read() on a package > (rapl/uncore) event that isn't currently scheduled in ends up doing an > out-of-bounds load. > > Rework the code to more explicitly deal with event->oncpu being -1. > > Reported-by: Alexei Starovoitov <[email protected]> > Cc: David Carrillo-Cisneros <[email protected]> > Cc: Stephane Eranian <[email protected]> > Fixes: d6a2f9035bfc ("perf/core: Introduce PMU_EV_CAP_READ_ACTIVE_PKG") > Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Thanks for the quick fix! Everything is clean after several hours. Tested-by: Alexei Starovoitov <[email protected]> > /* > * Purposely ignore the smp_call_function_single() return > @@ -3702,7 +3706,8 @@ static int perf_event_read(struct perf_event *event, > bool group) > * Therefore, either way, we'll have an up-to-date event count > * after this. > */ in that comment above (not shown in this diff) there is a line: "If event->oncpu isn't a valid CPU it means..." it doesn't match the code due to merge conflict resolution in 2cc538412a. Probably makes sense to fix it s/event->oncpu/event_cpu/ as part of this diff. > - (void)smp_call_function_single(cpu_to_read, __perf_event_read, > &data, 1); > + (void)smp_call_function_single(event_cpu, __perf_event_read, > &data, 1); > + preempt_enable(); > ret = data.ret; > } else if (event->state == PERF_EVENT_STATE_INACTIVE) { > struct perf_event_context *ctx = event->ctx;
