On Tue, Nov 15, 2016 at 12:57:31AM -0500, Vince Weaver wrote:
> On Mon, 14 Nov 2016, Vince Weaver wrote:
>
> > Anyway as per the suggestion at Linux Plumbers I enabled KASAN and on my
> > haswell machine it falls over in a few minutes of running the perf_fuzzer.
> >
> > [ 205.740194]
> > ==================================================================
> > [ 205.748005] BUG: KASAN: slab-out-of-bounds in
> > snb_uncore_imc_event_del+0x6c/0xa0 at addr ffff8800caa43768
> > [ 205.758324] Read of size 8 by task perf_fuzzer/6618
> > [ 205.763589] CPU: 0 PID: 6618 Comm: perf_fuzzer Not tainted 4.9.0-rc5 #4
> > [ 205.770721] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS FBKT72AUS
> > 01/26/2014
> > [ 205.778689] ffff8800c3c479b8 ffffffff816bb796 ffff88011ec00600
> > ffff8800caa43580
> > [ 205.786759] ffff8800c3c479e0 ffffffff812fb961 ffff8800c3c47a78
> > ffff8800caa43580
> > [ 205.794850] ffff8800caa43580 ffff8800c3c47a68 ffffffff812fbbd8
> > ffff8800c3c47a28
> > [ 205.802911] Call Trace:
> > [ 205.805559] [<ffffffff816bb796>] dump_stack+0x63/0x8d
> > [ 205.811135] [<ffffffff812fb961>] kasan_object_err+0x21/0x70
> > [ 205.817267] [<ffffffff812fbbd8>] kasan_report_error+0x1d8/0x4c0
> > [ 205.823752] [<ffffffff81133275>] ? __lock_is_held+0x75/0xc0
> > [ 205.829868] [<ffffffff81025b12>] ? snb_uncore_imc_read_counter+0x42/0x50
> > [ 205.837198] [<ffffffff810222e2>] ? uncore_perf_event_update+0xe2/0x160
> > [ 205.844337] [<ffffffff812fc319>] kasan_report+0x39/0x40
> > [ 205.850085] [<ffffffff81025e3c>] ? snb_uncore_imc_event_del+0x6c/0xa0
>
> The best I can tell this maps to:
>
> static void snb_uncore_imc_event_del(struct perf_event *event, int flags)
> {
> struct intel_uncore_box *box = uncore_event_to_box(event);
> int i;
>
> snb_uncore_imc_event_stop(event, PERF_EF_UPDATE);
>
> for (i = 0; i < box->n_events; i++) {
> >>> if (event == box->event_list[i]) {
> --box->n_events;
> break;
> }
> }
> }
>
> Can this code be right? Does it actually remove the event?
> The similar code in
>
> static void uncore_pmu_event_del(struct perf_event *event, int flags)
>
> ....
>
> for (i = 0; i < box->n_events; i++) {
> if (event == box->event_list[i]) {
> uncore_put_event_constraint(box, event);
>
> for (++i; i < box->n_events; i++)
> box->event_list[i - 1] = box->event_list[i];
>
> --box->n_events;
> break;
> }
> }
>
>
> seems like it is more likely to be correct.
Kan, can you look at this?
