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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 6A989C65BAF for ; Sun, 9 Dec 2018 22:21:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B4B62081F for ; Sun, 9 Dec 2018 22:21:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B4B62081F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk 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 S1727934AbeLIWVB (ORCPT ); Sun, 9 Dec 2018 17:21:01 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35352 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726541AbeLIVzY (ORCPT ); Sun, 9 Dec 2018 16:55:24 -0500 Received: from pub.yeoldevic.com ([81.174.156.145] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gW72n-0002pr-8f; Sun, 09 Dec 2018 21:55:21 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gW72k-0003dt-Ap; Sun, 09 Dec 2018 21:55:18 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Vince Weaver" , "Linus Torvalds" , "Stephane Eranian" , "Arnaldo Carvalho de Melo" , "Jiri Olsa" , "Thomas Gleixner" , "Andrew Vagin" , "Namhyung Kim" , "Jiri Olsa" , "Peter Zijlstra (Intel)" , "Alexander Shishkin" , "Arnaldo Carvalho de Melo" , "Ingo Molnar" Date: Sun, 09 Dec 2018 21:50:33 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 289/328] perf/ring_buffer: Prevent concurent ring buffer access In-Reply-To: X-SA-Exim-Connect-IP: 81.174.156.145 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Olsa commit cd6fb677ce7e460c25bdd66f689734102ec7d642 upstream. Some of the scheduling tracepoints allow the perf_tp_event code to write to ring buffer under different cpu than the code is running on. This results in corrupted ring buffer data demonstrated in following perf commands: # perf record -e 'sched:sched_switch,sched:sched_wakeup' perf bench sched messaging # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 0.383 [sec] [ perf record: Woken up 8 times to write data ] 0x42b890 [0]: failed to process type: -1765585640 [ perf record: Captured and wrote 4.825 MB perf.data (29669 samples) ] # perf report --stdio 0x42b890 [0]: failed to process type: -1765585640 The reason for the corruption are some of the scheduling tracepoints, that have __perf_task dfined and thus allow to store data to another cpu ring buffer: sched_waking sched_wakeup sched_wakeup_new sched_stat_wait sched_stat_sleep sched_stat_iowait sched_stat_blocked The perf_tp_event function first store samples for current cpu related events defined for tracepoint: hlist_for_each_entry_rcu(event, head, hlist_entry) perf_swevent_event(event, count, &data, regs); And then iterates events of the 'task' and store the sample for any task's event that passes tracepoint checks: ctx = rcu_dereference(task->perf_event_ctxp[perf_sw_context]); list_for_each_entry_rcu(event, &ctx->event_list, event_entry) { if (event->attr.type != PERF_TYPE_TRACEPOINT) continue; if (event->attr.config != entry->type) continue; perf_swevent_event(event, count, &data, regs); } Above code can race with same code running on another cpu, ending up with 2 cpus trying to store under the same ring buffer, which is specifically not allowed. This patch prevents the problem, by allowing only events with the same current cpu to receive the event. NOTE: this requires the use of (per-task-)per-cpu buffers for this feature to work; perf-record does this. Signed-off-by: Jiri Olsa [peterz: small edits to Changelog] Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Andrew Vagin Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Fixes: e6dab5ffab59 ("perf/trace: Add ability to set a target task for events") Link: http://lkml.kernel.org/r/20180923161343.GB15054@krava Signed-off-by: Ingo Molnar Signed-off-by: Ben Hutchings --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6276,6 +6276,8 @@ void perf_tp_event(u64 addr, u64 count, goto unlock; list_for_each_entry_rcu(event, &ctx->event_list, event_entry) { + if (event->cpu != smp_processor_id()) + continue; if (event->attr.type != PERF_TYPE_TRACEPOINT) continue; if (event->attr.config != entry->type)