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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 F40F6C6778C for ; Sun, 1 Jul 2018 16:19:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE59724461 for ; Sun, 1 Jul 2018 16:19:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE59724461 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753463AbeGAQTD (ORCPT ); Sun, 1 Jul 2018 12:19:03 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33124 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753217AbeGAQS7 (ORCPT ); Sun, 1 Jul 2018 12:18:59 -0400 Received: from localhost (LFbn-1-12247-202.w90-92.abo.wanadoo.fr [90.92.61.202]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 9BD9B86A; Sun, 1 Jul 2018 16:18:58 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mauro Carvalho Chehab Subject: [PATCH 4.4 089/105] media: dvb_frontend: fix locking issues at dvb_frontend_get_event() Date: Sun, 1 Jul 2018 18:02:39 +0200 Message-Id: <20180701153155.855633462@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180701153149.382300170@linuxfoundation.org> References: <20180701153149.382300170@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review 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 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mauro Carvalho Chehab commit 76d81243a487c09619822ef8e7201a756e58a87d upstream. As warned by smatch: drivers/media/dvb-core/dvb_frontend.c:314 dvb_frontend_get_event() warn: inconsistent returns 'sem:&fepriv->sem'. Locked on: line 288 line 295 line 306 line 314 Unlocked on: line 303 The lock implementation for get event is wrong, as, if an interrupt occurs, down_interruptible() will fail, and the routine will call up() twice when userspace calls the ioctl again. The bad code is there since when Linux migrated to git, in 2005. Cc: stable@vger.kernel.org Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/dvb-core/dvb_frontend.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) --- a/drivers/media/dvb-core/dvb_frontend.c +++ b/drivers/media/dvb-core/dvb_frontend.c @@ -230,8 +230,20 @@ static void dvb_frontend_add_event(struc wake_up_interruptible (&events->wait_queue); } +static int dvb_frontend_test_event(struct dvb_frontend_private *fepriv, + struct dvb_fe_events *events) +{ + int ret; + + up(&fepriv->sem); + ret = events->eventw != events->eventr; + down(&fepriv->sem); + + return ret; +} + static int dvb_frontend_get_event(struct dvb_frontend *fe, - struct dvb_frontend_event *event, int flags) + struct dvb_frontend_event *event, int flags) { struct dvb_frontend_private *fepriv = fe->frontend_priv; struct dvb_fe_events *events = &fepriv->events; @@ -249,13 +261,8 @@ static int dvb_frontend_get_event(struct if (flags & O_NONBLOCK) return -EWOULDBLOCK; - up(&fepriv->sem); - - ret = wait_event_interruptible (events->wait_queue, - events->eventw != events->eventr); - - if (down_interruptible (&fepriv->sem)) - return -ERESTARTSYS; + ret = wait_event_interruptible(events->wait_queue, + dvb_frontend_test_event(fepriv, events)); if (ret < 0) return ret;