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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 A324CC35242 for ; Sat, 8 Feb 2020 18:30:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 870C124125 for ; Sat, 8 Feb 2020 18:30:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728036AbgBHSaD (ORCPT ); Sat, 8 Feb 2020 13:30:03 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33862 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727786AbgBHS3k (ORCPT ); Sat, 8 Feb 2020 13:29:40 -0500 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1j0UrH-0003dS-IH; Sat, 08 Feb 2020 18:29:35 +0000 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1j0UrG-000CMw-GZ; Sat, 08 Feb 2020 18:29:34 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Chanwoo Choi" , "Leonard Crestez" , "Matthias Kaehlcke" Date: Sat, 08 Feb 2020 18:19:55 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 056/148] PM / devfreq: Lock devfreq in trans_stat_show In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.82-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Leonard Crestez commit 2abb0d5268ae7b5ddf82099b1f8d5aa8414637d4 upstream. There is no locking in this sysfs show function so stats printing can race with a devfreq_update_status called as part of freq switching or with initialization. Also add an assert in devfreq_update_status to make it clear that lock must be held by caller. Fixes: 39688ce6facd ("PM / devfreq: account suspend/resume for stats") Signed-off-by: Leonard Crestez Reviewed-by: Matthias Kaehlcke Reviewed-by: Chanwoo Choi Signed-off-by: Chanwoo Choi [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -95,6 +95,7 @@ static int devfreq_update_status(struct int lev, prev_lev, ret = 0; unsigned long cur_time; + lockdep_assert_held(&devfreq->lock); cur_time = jiffies; prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq); @@ -1054,9 +1055,13 @@ static ssize_t trans_stat_show(struct de int i, j; unsigned int max_state = devfreq->profile->max_state; + mutex_lock(&devfreq->lock); if (!devfreq->stop_polling && - devfreq_update_status(devfreq, devfreq->previous_freq)) + devfreq_update_status(devfreq, devfreq->previous_freq)) { + mutex_unlock(&devfreq->lock); return 0; + } + mutex_unlock(&devfreq->lock); len = sprintf(buf, " From : To\n"); len += sprintf(buf + len, " :");