Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752244AbbEHEUf (ORCPT ); Fri, 8 May 2015 00:20:35 -0400 Received: from mail-qk0-f176.google.com ([209.85.220.176]:34981 "EHLO mail-qk0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbbEHEUb (ORCPT ); Fri, 8 May 2015 00:20:31 -0400 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Fri, 8 May 2015 00:25:50 -0400 (EDT) To: Peter Zijlstra cc: Stephane Eranian , Vince Weaver , LKML , Arnaldo Carvalho de Melo , Jiri Olsa , Ingo Molnar , Paul Mackerras Subject: Re: perf: fuzzer triggers NULL pointer derefreence in x86_schedule_events In-Reply-To: <20150507124300.GK23123@twins.programming.kicks-ass.net> Message-ID: References: <20150501125955.GF5029@twins.programming.kicks-ass.net> <20150507124300.GK23123@twins.programming.kicks-ass.net> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1000 Lines: 26 On Thu, 7 May 2015, Peter Zijlstra wrote: > Indeed so; and we can make an analogous argument for hwc. However: > > > I think it is more likely related to the bitmask (idxmsk). But then > > it is always allocated with the constraint even with the HT bug > > workaround. So most, likely the index is bogus and you touch outside > > the idxmsk[] array. > > [428232.701319] BUG: unable to handle kernel NULL pointer dereference at (null) > > But the thing really tried to touch NULL, not some random address that > faulted. > > As always, Vince has found us a good puzzle ;-) and sorry I haven't been much help tracking it down. I'm trying to trigger it again, but this particular bug only pops up after a week or so of fuzzing. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/