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=-9.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 A9551C46475 for ; Thu, 25 Oct 2018 14:16:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6BB5B20870 for ; Thu, 25 Oct 2018 14:16:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="UdzJNWno" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6BB5B20870 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 S1729362AbeJYWtW (ORCPT ); Thu, 25 Oct 2018 18:49:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:58416 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729324AbeJYWtU (ORCPT ); Thu, 25 Oct 2018 18:49:20 -0400 Received: from sasha-vm.mshome.net (unknown [167.98.65.38]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5FBB121479; Thu, 25 Oct 2018 14:16:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1540476983; bh=e+ZiUDZJrBdgPJQ5sjPTNLBtQLzmGLahdZguLaJpF+A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UdzJNWno2ZrPpG1BKMUNpTdzOEYQ1zVWb1Ccit9UGzwgGSmcdwZQ9fvDGM51AKidU w5SBsBnusKSjRPV1+SDAtDRVG7XITUsPhI1E7kqNNsZ7cewagGCdBmMmNx+x1TjBMp pJEw1tD2/eGveSZO6SwHJYgW/jHzy/T68KVLMEJw= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jiri Olsa , Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Peter Zijlstra , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL 4.9 81/98] perf/core: Fix locking for children siblings group read Date: Thu, 25 Oct 2018 10:14:06 -0400 Message-Id: <20181025141423.213774-81-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181025141423.213774-1-sashal@kernel.org> References: <20181025141423.213774-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Olsa [ Upstream commit 2aeb1883547626d82c597cce2c99f0b9c62e2425 ] We're missing ctx lock when iterating children siblings within the perf_read path for group reading. Following race and crash can happen: User space doing read syscall on event group leader: T1: perf_read lock event->ctx->mutex perf_read_group lock leader->child_mutex __perf_read_group_add(child) list_for_each_entry(sub, &leader->sibling_list, group_entry) ----> sub might be invalid at this point, because it could get removed via perf_event_exit_task_context in T2 Child exiting and cleaning up its events: T2: perf_event_exit_task_context lock ctx->mutex list_for_each_entry_safe(child_event, next, &child_ctx->event_list,... perf_event_exit_event(child) lock ctx->lock perf_group_detach(child) unlock ctx->lock ----> child is removed from sibling_list without any sync with T1 path above ... free_event(child) Before the child is removed from the leader's child_list, (and thus is omitted from perf_read_group processing), we need to ensure that perf_read_group touches child's siblings under its ctx->lock. Peter further notes: | One additional note; this bug got exposed by commit: | | ba5213ae6b88 ("perf/core: Correct event creation with PERF_FORMAT_GROUP") | | which made it possible to actually trigger this code-path. Tested-by: Andi Kleen Signed-off-by: Jiri Olsa Acked-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: ba5213ae6b88 ("perf/core: Correct event creation with PERF_FORMAT_GROUP") Link: http://lkml.kernel.org/r/20170720141455.2106-1-jolsa@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/events/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 95bd00d9f2c3..06b359af4322 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4331,7 +4331,9 @@ EXPORT_SYMBOL_GPL(perf_event_read_value); static int __perf_read_group_add(struct perf_event *leader, u64 read_format, u64 *values) { + struct perf_event_context *ctx = leader->ctx; struct perf_event *sub; + unsigned long flags; int n = 1; /* skip @nr */ int ret; @@ -4361,12 +4363,15 @@ static int __perf_read_group_add(struct perf_event *leader, if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(leader); + raw_spin_lock_irqsave(&ctx->lock, flags); + list_for_each_entry(sub, &leader->sibling_list, group_entry) { values[n++] += perf_event_count(sub); if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(sub); } + raw_spin_unlock_irqrestore(&ctx->lock, flags); return 0; } -- 2.17.1