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,URIBL_BLOCKED,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 2E5D2CA9EC9 for ; Mon, 4 Nov 2019 22:25:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EDF2020650 for ; Mon, 4 Nov 2019 22:25:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572906313; bh=nk4O2gxrkdy69/8sNMd0ZPESLXqQN5sMW0ezN6AV+RQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=A3Fw1TC2RBBBQDkAhgDK7bUlhb5fJxRcZ5x6DVnOokqN3b37aU1f/szcFR/RAY1bt QWUzpaV7QRXz4xtwWATe388hWGvEM2bU6mdycnfK9Ic7bZt4QSjjpw2DM1QZMEerls pTEMp3ii0XL6RAklYB91W5TWxMGRNMq6es90dCvw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388136AbfKDWZM (ORCPT ); Mon, 4 Nov 2019 17:25:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:45052 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730624AbfKDVv4 (ORCPT ); Mon, 4 Nov 2019 16:51:56 -0500 Received: from localhost (6.204-14-84.ripe.coltfrance.com [84.14.204.6]) (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 3A8A82053B; Mon, 4 Nov 2019 21:51:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904315; bh=nk4O2gxrkdy69/8sNMd0ZPESLXqQN5sMW0ezN6AV+RQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WCu6LgkYmQTIJlAJDy0sASikxb5YKr33No+tZ9Lz6UThcnp9kgeW8af7S+D9OvZZc o5qe4WAXPbhCGumoYM5GHDjKKZ+ATCWRUKwpmcZbgGqgniqTyYLuHeBhawjQ5cMZYi 09nhhUFpZvpikatrDkbhU6JOB+eAjy56O+c3nVH8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai , Sasha Levin , "Kirill A . Shutemov" Subject: [PATCH 4.9 62/62] ALSA: timer: Fix mutex deadlock at releasing card Date: Mon, 4 Nov 2019 22:45:24 +0100 Message-Id: <20191104212001.419204692@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104211901.387893698@linuxfoundation.org> References: <20191104211901.387893698@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: Takashi Iwai [ Upstream commit a39331867335d4a94b6165e306265c9e24aca073 ] When a card is disconnected while in use, the system waits until all opened files are closed then releases the card. This is done via put_device() of the card device in each device release code. The recently reported mutex deadlock bug happens in this code path; snd_timer_close() for the timer device deals with the global register_mutex and it calls put_device() there. When this timer device is the last one, the card gets freed and it eventually calls snd_timer_free(), which has again the protection with the global register_mutex -- boom. Basically put_device() call itself is race-free, so a relative simple workaround is to move this put_device() call out of the mutex. For achieving that, in this patch, snd_timer_close_locked() got a new argument to store the card device pointer in return, and each caller invokes put_device() with the returned object after the mutex unlock. Reported-and-tested-by: Kirill A. Shutemov Cc: Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/timer.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/sound/core/timer.c b/sound/core/timer.c index 6eb4e97662d9c..19d90aa082184 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -239,7 +239,8 @@ static int snd_timer_check_master(struct snd_timer_instance *master) return 0; } -static int snd_timer_close_locked(struct snd_timer_instance *timeri); +static int snd_timer_close_locked(struct snd_timer_instance *timeri, + struct device **card_devp_to_put); /* * open a timer instance @@ -251,6 +252,7 @@ int snd_timer_open(struct snd_timer_instance **ti, { struct snd_timer *timer; struct snd_timer_instance *timeri = NULL; + struct device *card_dev_to_put = NULL; int err; mutex_lock(®ister_mutex); @@ -274,7 +276,7 @@ int snd_timer_open(struct snd_timer_instance **ti, list_add_tail(&timeri->open_list, &snd_timer_slave_list); err = snd_timer_check_slave(timeri); if (err < 0) { - snd_timer_close_locked(timeri); + snd_timer_close_locked(timeri, &card_dev_to_put); timeri = NULL; } goto unlock; @@ -326,7 +328,7 @@ int snd_timer_open(struct snd_timer_instance **ti, timeri = NULL; if (timer->card) - put_device(&timer->card->card_dev); + card_dev_to_put = &timer->card->card_dev; module_put(timer->module); goto unlock; } @@ -336,12 +338,15 @@ int snd_timer_open(struct snd_timer_instance **ti, timer->num_instances++; err = snd_timer_check_master(timeri); if (err < 0) { - snd_timer_close_locked(timeri); + snd_timer_close_locked(timeri, &card_dev_to_put); timeri = NULL; } unlock: mutex_unlock(®ister_mutex); + /* put_device() is called after unlock for avoiding deadlock */ + if (card_dev_to_put) + put_device(card_dev_to_put); *ti = timeri; return err; } @@ -351,7 +356,8 @@ EXPORT_SYMBOL(snd_timer_open); * close a timer instance * call this with register_mutex down. */ -static int snd_timer_close_locked(struct snd_timer_instance *timeri) +static int snd_timer_close_locked(struct snd_timer_instance *timeri, + struct device **card_devp_to_put) { struct snd_timer *timer = NULL; struct snd_timer_instance *slave, *tmp; @@ -403,7 +409,7 @@ static int snd_timer_close_locked(struct snd_timer_instance *timeri) timer->hw.close(timer); /* release a card refcount for safe disconnection */ if (timer->card) - put_device(&timer->card->card_dev); + *card_devp_to_put = &timer->card->card_dev; module_put(timer->module); } @@ -415,14 +421,18 @@ static int snd_timer_close_locked(struct snd_timer_instance *timeri) */ int snd_timer_close(struct snd_timer_instance *timeri) { + struct device *card_dev_to_put = NULL; int err; if (snd_BUG_ON(!timeri)) return -ENXIO; mutex_lock(®ister_mutex); - err = snd_timer_close_locked(timeri); + err = snd_timer_close_locked(timeri, &card_dev_to_put); mutex_unlock(®ister_mutex); + /* put_device() is called after unlock for avoiding deadlock */ + if (card_dev_to_put) + put_device(card_dev_to_put); return err; } EXPORT_SYMBOL(snd_timer_close); -- 2.20.1