Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753697AbbEANAT (ORCPT ); Fri, 1 May 2015 09:00:19 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:53562 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbbEANAR (ORCPT ); Fri, 1 May 2015 09:00:17 -0400 Date: Fri, 1 May 2015 14:59:55 +0200 From: Peter Zijlstra To: Vince Weaver Cc: linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Jiri Olsa , Ingo Molnar , Paul Mackerras , Stephane Eranian Subject: Re: perf: fuzzer triggers NULL pointer derefreence in x86_schedule_events Message-ID: <20150501125955.GF5029@twins.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1056 Lines: 29 On Thu, Apr 30, 2015 at 03:08:56PM -0400, Vince Weaver wrote: > > So the perf_fuzzer caught this after about a week of fuzzing on a Haswell > machine running a recent git kernel (pre 4.1-rc1 though). > > We've seen this BUG before and various fixes were applied but apparently > it wasn't enough. > > Sadly it doesn't seem to be reproducible. > > validate_group() -> x86_pmu.schedule_events() -> ???? -> variable_test_bit() > (hard to tell which test bit with all the inlining going on). Assuming you build with debug info addr2line -i can help, but I think I found it by comparing the Code section below with my objdump -D output. Its: /* constraint still honored */ if (!test_bit(hwc->idx, c->idxmsk)) break; Which would seem to suggest c is NULL. Lemme go figure out how that could happen. -- 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/