Re: perf_fuzzer crash on pentium 4

Vince Weaver
2014-05-06T21:26:46Z

On Wed, 7 May 2014, Cyrill Gorcunov wrote:

> > [ 67.872274] BUG: unable to handle kernel NULL pointer dereference at 00000004
> > [ 67.876146] IP: [<ffffffff81013df2>] p4_pmu_schedule_events+0xa5/0x331
>
> This looks like
>
> p4_pmu_schedule_events:
> ...
> bind = p4_config_get_bind(hwc->config);
> returned bind = NULL;
> escr_idx = p4_get_escr_idx(bind->escr_msr[thread]); NULL deref
>
> If i'm right (btw it's possible to use addr2line helper?)

Yes, the address maps to

escr_idx = p4_get_escr_idx(bind->escr_msr[thread]);

> then hwc->config
> is corrupted and p4_config_get_bind returned nil simply because proper event
> was not found. And I don't understand how it could happen because before
> configuration gets written into hwc->config it's validated once obtained
> from user-space as a raw event. Weird...

I'll try to get some sort of trace out if it to see what event is being
tried.

Vince