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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 EC959C2D0DB for ; Sun, 26 Jan 2020 19:20:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C4D2120842 for ; Sun, 26 Jan 2020 19:20:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729052AbgAZTUW (ORCPT ); Sun, 26 Jan 2020 14:20:22 -0500 Received: from mail.kernel.org ([198.145.29.99]:53606 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726382AbgAZTUW (ORCPT ); Sun, 26 Jan 2020 14:20:22 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 B088F20716; Sun, 26 Jan 2020 19:20:21 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1ivnSG-000zq4-KB; Sun, 26 Jan 2020 14:20:20 -0500 Message-Id: <20200126192020.508349799@goodmis.org> User-Agent: quilt/0.65 Date: Sun, 26 Jan 2020 14:19:33 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Luis Henriques Subject: [for-next][PATCH 1/7] tracing: Fix very unlikely race of registering two stat tracers References: <20200126191932.984391723@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" Looking through old emails in my INBOX, I came across a patch from Luis Henriques that attempted to fix a race of two stat tracers registering the same stat trace (extremely unlikely, as this is done in the kernel, and probably doesn't even exist). The submitted patch wasn't quite right as it needed to deal with clean up a bit better (if two stat tracers were the same, it would have the same files). But to make the code cleaner, all we needed to do is to keep the all_stat_sessions_mutex held for most of the registering function. Link: http://lkml.kernel.org/r/1410299375-20068-1-git-send-email-luis.henriques@canonical.com Fixes: 002bb86d8d42f ("tracing/ftrace: separate events tracing and stats tracing engine") Reported-by: Luis Henriques Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_stat.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c index 874f1274cf99..da8a38c3d5e4 100644 --- a/kernel/trace/trace_stat.c +++ b/kernel/trace/trace_stat.c @@ -304,7 +304,7 @@ static int init_stat_file(struct stat_session *session) int register_stat_tracer(struct tracer_stat *trace) { struct stat_session *session, *node; - int ret; + int ret = -EINVAL; if (!trace) return -EINVAL; @@ -315,17 +315,15 @@ int register_stat_tracer(struct tracer_stat *trace) /* Already registered? */ mutex_lock(&all_stat_sessions_mutex); list_for_each_entry(node, &all_stat_sessions, session_list) { - if (node->ts == trace) { - mutex_unlock(&all_stat_sessions_mutex); - return -EINVAL; - } + if (node->ts == trace) + goto out; } - mutex_unlock(&all_stat_sessions_mutex); + ret = -ENOMEM; /* Init the session */ session = kzalloc(sizeof(*session), GFP_KERNEL); if (!session) - return -ENOMEM; + goto out; session->ts = trace; INIT_LIST_HEAD(&session->session_list); @@ -334,15 +332,16 @@ int register_stat_tracer(struct tracer_stat *trace) ret = init_stat_file(session); if (ret) { destroy_session(session); - return ret; + goto out; } + ret = 0; /* Register */ - mutex_lock(&all_stat_sessions_mutex); list_add_tail(&session->session_list, &all_stat_sessions); + out: mutex_unlock(&all_stat_sessions_mutex); - return 0; + return ret; } void unregister_stat_tracer(struct tracer_stat *trace) -- 2.24.1