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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 23CE1C3B1B5 for ; Fri, 14 Feb 2020 18:17:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF8C12168B for ; Fri, 14 Feb 2020 18:17:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581704267; bh=vs9jAO3/iw7R1mvmvAtc60BtnED6zWOu2HDmfa45RQ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=IxL6NSHbgTZkJqiicAjBIJVBNcQoPD1KRES0UzqgsNCF/QTkU+J39z4FZVZ+p4JXS Zk+4XJ8xBhuVJxD4IVxAQV4F+N49LFugmZgGgDjwIn1/AIgHARIqYsK2NClN8jq5vx +unPvO2f0/KC2yWU6V/H7Gm+SxIgLOkpWs/0E0mE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730668AbgBNPvH (ORCPT ); Fri, 14 Feb 2020 10:51:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:55854 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730147AbgBNPvH (ORCPT ); Fri, 14 Feb 2020 10:51:07 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 479D5217F4; Fri, 14 Feb 2020 15:51:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581695466; bh=vs9jAO3/iw7R1mvmvAtc60BtnED6zWOu2HDmfa45RQ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oi+engCQ5HhiC2WetV7TVv4C2PnMvX6nrloK5/RobJmTK8IMIEM0FTVCkp5bgxf9B zzwuPIMLnWd6yACD0L301/4WXMAI5nJrgUP9+Mb4hKFKCPejoa5fjWJKfVwii5Ef1M K5umBjsg3+TxaMOADGpwV3l2l8z5OloKusumuurA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Steven Rostedt (VMware)" , Luis Henriques , Sasha Levin Subject: [PATCH AUTOSEL 5.5 102/542] tracing: Fix very unlikely race of registering two stat tracers Date: Fri, 14 Feb 2020 10:41:34 -0500 Message-Id: <20200214154854.6746-102-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214154854.6746-1-sashal@kernel.org> References: <20200214154854.6746-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Steven Rostedt (VMware)" [ Upstream commit dfb6cd1e654315168e36d947471bd2a0ccd834ae ] 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) Signed-off-by: Sasha Levin --- 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 2b4d6e674d876..d1fa19773cc8e 100644 --- a/kernel/trace/trace_stat.c +++ b/kernel/trace/trace_stat.c @@ -308,7 +308,7 @@ 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; @@ -319,17 +319,15 @@ 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); @@ -338,15 +336,16 @@ 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) -- 2.20.1