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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 680DBC35E15 for ; Thu, 27 Feb 2020 13:41:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4016820726 for ; Thu, 27 Feb 2020 13:41:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582810880; bh=/uhP3ZwQ5abxbXuZsmYwVHtt+b2kPXwWmXQHgMYq7mE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HB3JWQQrhrdQWUEJoM7n4oRbbyB0oxOvfS2vglnOD9fCb0PooDkM4ctJsQkml937L mJ4BoscEoX3aDafbgO3Qnu6qhBnXomqan431uLxScmHy/sLphjfip7qyrmTb+4HeGW ayzoAkujCSQIyEGX6IjbxZPu8F0o1RgQfk7GGEQY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729558AbgB0NlT (ORCPT ); Thu, 27 Feb 2020 08:41:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:35800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729502AbgB0NlN (ORCPT ); Thu, 27 Feb 2020 08:41:13 -0500 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 617D720578; Thu, 27 Feb 2020 13:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582810872; bh=/uhP3ZwQ5abxbXuZsmYwVHtt+b2kPXwWmXQHgMYq7mE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NIZSOCCIUIDujhnp2jd/zo8FcYW15IJFDSZ7sx9D1GdimWElmWeP8ToBs3G94Ep/S rzw8kyQtxjAinhQhnJl+GksTkuPsV2rzFFGI3ycZOSThBojos2eKIdzK0IJ+PYhicZ YFrvPe9ZR7Ium+883S0rg/nGd15fvgb/NRKPJnlg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luis Henriques , "Steven Rostedt (VMware)" , Sasha Levin Subject: [PATCH 4.4 031/113] tracing: Fix very unlikely race of registering two stat tracers Date: Thu, 27 Feb 2020 14:35:47 +0100 Message-Id: <20200227132216.707719460@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200227132211.791484803@linuxfoundation.org> References: <20200227132211.791484803@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 6cf9353167696..a2081a7f0c2cd 100644 --- a/kernel/trace/trace_stat.c +++ b/kernel/trace/trace_stat.c @@ -302,7 +302,7 @@ 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; @@ -313,17 +313,15 @@ 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); @@ -332,15 +330,16 @@ 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