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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,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 BC966C433E0 for ; Thu, 30 Jul 2020 08:11:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95E0E2083B for ; Thu, 30 Jul 2020 08:11:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596096660; bh=ocQitoteaM9KCkLV7fP43lZRJgiX38p88GYiGm/HNN0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bpPE7yJb6l+qwznLLiaSK7fDhZNST1vegwi3IZPatIa2jox19XF9RPzmO18oVMvWC b32udZv17soayluV2k79SK9L70cirJ4FnxZ9T71EBMCgfk/y+14sM6RYXOJkjKo6N2 wYJ4T+mFqc7D9FcAZQQ0VKO/WcK/LEJxcRD2CBNY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729357AbgG3IK7 (ORCPT ); Thu, 30 Jul 2020 04:10:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:50036 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729901AbgG3IK5 (ORCPT ); Thu, 30 Jul 2020 04:10:57 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 566512074B; Thu, 30 Jul 2020 08:10:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596096655; bh=ocQitoteaM9KCkLV7fP43lZRJgiX38p88GYiGm/HNN0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1MlUOWn8/j2vVFDmX23TLgKU82H1iYne5WnQfnMrvvmf2fO/1QnFkOcrS5WXd8/Z1 kXchJRYizH21UzHWz6zAHZqAV6BnQ0l+VgtDz8IGUm2K1GSi6pXt5SRqtNLX28ATIb 1+5q1rWzUKi5MpXRW3uyNMgAtOk8ib09GdLPQYsI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andi Kleen , Jiri Olsa , "Peter Zijlstra (Intel)" , Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Guenter Roeck Subject: [PATCH 4.4 10/54] perf/core: Fix locking for children siblings group read Date: Thu, 30 Jul 2020 10:04:49 +0200 Message-Id: <20200730074421.712538730@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200730074421.203879987@linuxfoundation.org> References: <20200730074421.203879987@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jiri Olsa commit 2aeb1883547626d82c597cce2c99f0b9c62e2425 upstream. 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 Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3940,7 +3940,9 @@ 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; @@ -3970,12 +3972,15 @@ static int __perf_read_group_add(struct 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; }