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=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 526DBC3B1A6 for ; Fri, 14 Feb 2020 17:11:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C80B2086A for ; Fri, 14 Feb 2020 17:11:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581700270; bh=BU4zdI+Om8I7i8HgMQTLxfaZ1cBg4dQ+Il+MUW2HDJU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YEQ1gvWEukiorF6ke53+6PAVFk4pV1B36LrhCAmvuoREoPMP9fSCzhAXkdE9S28pp A1W060BblRd51Tc4cfIGyB7sgdEC5ThLkxpDQatYjab0wfXZfQWFIALEwIgumz61UO 6+HFB9MoJsrgoEaq3MBHx61K322HeiNkgsJqC6Vo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403887AbgBNQN3 (ORCPT ); Fri, 14 Feb 2020 11:13:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:40400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391674AbgBNQMm (ORCPT ); Fri, 14 Feb 2020 11:12:42 -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 566292469F; Fri, 14 Feb 2020 16:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581696762; bh=BU4zdI+Om8I7i8HgMQTLxfaZ1cBg4dQ+Il+MUW2HDJU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gJbjqAJOG+qrteCBXln7G347hoHx2MPEpFRSXY0KWqyN8lAoRxd30oKe0t3u8mBbE F29YUbolRaN9xPLsAXyZ9bBss5x6yP9hLDFShGRn7L3TWTsF+kTyCTjXHxUdQKUCrr T9C+w/gEvc+hxRbBTSSR84hYc0bFcareaBJbAxtM= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Steven Rostedt (VMware)" , Luis Henriques , Sasha Levin Subject: [PATCH AUTOSEL 4.19 042/252] tracing: Fix very unlikely race of registering two stat tracers Date: Fri, 14 Feb 2020 11:08:17 -0500 Message-Id: <20200214161147.15842-42-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214161147.15842-1-sashal@kernel.org> References: <20200214161147.15842-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 bf68af63538b4..92b76f9e25edd 100644 --- a/kernel/trace/trace_stat.c +++ b/kernel/trace/trace_stat.c @@ -306,7 +306,7 @@ 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; @@ -317,17 +317,15 @@ 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); @@ -336,15 +334,16 @@ 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