From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61195C43610 for ; Wed, 21 Nov 2018 10:16:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32B2020989 for ; Wed, 21 Nov 2018 10:16:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 32B2020989 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729972AbeKUUuK (ORCPT ); Wed, 21 Nov 2018 15:50:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51968 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbeKUUuJ (ORCPT ); Wed, 21 Nov 2018 15:50:09 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7DAA5356D3; Wed, 21 Nov 2018 10:16:19 +0000 (UTC) Received: from krava.brq.redhat.com (unknown [10.43.17.92]) by smtp.corp.redhat.com (Postfix) with ESMTP id C60F117CCB; Wed, 21 Nov 2018 10:16:17 +0000 (UTC) From: Jiri Olsa To: Peter Zijlstra Cc: lkml , Ingo Molnar , Alexander Shishkin , Arnaldo Carvalho de Melo , Andi Kleen , Vince Weaver Subject: [PATCH 3/3] perf/x86/intel: Disallow precise_ip on BTS event Date: Wed, 21 Nov 2018 11:16:12 +0100 Message-Id: <20181121101612.16272-3-jolsa@kernel.org> In-Reply-To: <20181121101612.16272-1-jolsa@kernel.org> References: <20181121101612.16272-1-jolsa@kernel.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 21 Nov 2018 10:16:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vince reported crash in bts flush code when touching the callchain data, which was supposed to be initialized as an 'early' callchain, but intel_pmu_drain_bts_buffer does not do that. BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 ... Call Trace: intel_pmu_drain_bts_buffer+0x151/0x220 ? intel_get_event_constraints+0x219/0x360 ? perf_assign_events+0xe2/0x2a0 ? select_idle_sibling+0x22/0x3a0 ? __update_load_avg_se+0x1ec/0x270 ? enqueue_task_fair+0x377/0xdd0 ? cpumask_next_and+0x19/0x20 ? load_balance+0x134/0x950 ? check_preempt_curr+0x7a/0x90 ? ttwu_do_wakeup+0x19/0x140 x86_pmu_stop+0x3b/0x90 x86_pmu_del+0x57/0x160 event_sched_out.isra.106+0x81/0x170 group_sched_out.part.108+0x51/0xc0 __perf_event_disable+0x7f/0x160 event_function+0x8c/0xd0 remote_function+0x3c/0x50 flush_smp_call_function_queue+0x35/0xe0 smp_call_function_single_interrupt+0x3a/0xd0 call_function_single_interrupt+0xf/0x20 It was triggered by fuzzer but can be easily reproduced by: # perf record -e cpu/branch-instructions/pu -g -c 1 Peter suggested not to allow branch tracing for precise events: > Now arguably, this is really stupid behaviour. Who in his right mind > wants callchain output on BTS entries. And even if they do, BTS + > precise_ip is nonsensical. > > So in my mind disallowing precise_ip on BTS would be the simplest fix. Suggested-by: Peter Zijlstra Fixes: 6cbc304f2f36 ("perf/x86/intel: Fix unwind errors from PEBS entries (mk-II)") Reported-by: Vince Weaver Signed-off-by: Jiri Olsa --- arch/x86/events/intel/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 3fd3842571e8..284893373d69 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3102,6 +3102,10 @@ static int intel_pmu_bts_config(struct perf_event *event) if (!attr->exclude_kernel) return -EOPNOTSUPP; + /* BTS is not allowed for precise events. */ + if (attr->precise_ip) + return -EOPNOTSUPP; + /* disallow bts if conflicting events are present */ if (x86_add_exclusive(x86_lbr_exclusive_lbr)) return -EBUSY; -- 2.17.2