From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1182439-1521807364-2-12426551830719074060 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1521807364; b=sObuS8tfqsbHkE81SxlfDKIwFsTEHcgPGO7qdvfrmshOZTP UaQE/TZ+0oTIMHLObXadBS1J1L4tv7jSG9N98fo7G+1wUnSDhsmb3s8UT41abVDc 5wMyZyfHrH5tU6jEXP8Qx9VQbzFwZw49O1j6VH/7CF9/oQ1IRbTHi5dywVOQ3YA8 lJvs+csesSTYFUmW7OT51OFxGXVzoN0XJir+CmTlEGEzZeHXrwkmxU8dbghv8Uka OGBjV7P9Q6sL+Ux/nvUFLB+XHzsoYM1Jso9Cft9BRYehfWXWxhgDYBYNGIUoJApJ b3Pgn4+Jfvgo7RssZCD8RTCpFK2ZWf7iYnrMjww== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-type:sender :list-id; s=arctest; t=1521807364; bh=LrfZaTtgAjLTS9ZvcgzX0AoecR xn2Q0/FMgDrSRj97g=; b=IZqn8xUmDSRT2d1aonk5ERSdbFUpebYouplknpblRL 4Eqw6M7iyOz/quZgFQyh9Ho5zxYXGxSQ2fAZlUuxijfkGi0svvc9qF9joMr3q5z4 1An5s/5eO8wDVfoL5avtEkYJu5IIKf5MkH5MpC8IhZKooEebQ7Z2aQBOH+6s8In5 E/MoIzbCimkjHYrZXuSPMR90+tdCZCUTpVGcYOLrsppM+TK2c/nd82KnMJrPYO2v PQmC9fgxkNJNwWiIdJZU6vCVeVLsIYKMsb+dsANsWWKuXczOy3gsAs6hJ3xL6BaN Hp8jIYqya24I4ocnLcPI9/iO8UTieO9tH4XZKag1HS3A== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752783AbeCWMPs (ORCPT ); Fri, 23 Mar 2018 08:15:48 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34110 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752166AbeCWJ4t (ORCPT ); Fri, 23 Mar 2018 05:56:49 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guenter Roeck , Wim Van Sebroeck , Sasha Levin Subject: [PATCH 4.15 26/84] watchdog: Fix potential kref imbalance when opening watchdog Date: Fri, 23 Mar 2018 10:53:40 +0100 Message-Id: <20180323095415.845552638@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180323095411.913234798@linuxfoundation.org> References: <20180323095411.913234798@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Guenter Roeck [ Upstream commit 4bcd615fad6adddc68b058d498b30a9e0e0db77a ] If a watchdog driver's open function sets WDOG_HW_RUNNING with the expectation that the watchdog can not be stopped, but then stops the watchdog anyway in its stop function, kref_get() wil not be called in watchdog_open(). If the watchdog then stops on close, WDOG_HW_RUNNING will be cleared and kref_put() will be called, causing a kref imbalance. As result the character device data structure will be released, which in turn will cause the system to crash on the next call to watchdog_open(). Fixes: ee142889e32f5 ("watchdog: Introduce WDOG_HW_RUNNING flag") Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/watchdog/watchdog_dev.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -769,6 +769,7 @@ static int watchdog_open(struct inode *i { struct watchdog_core_data *wd_data; struct watchdog_device *wdd; + bool hw_running; int err; /* Get the corresponding watchdog device */ @@ -788,7 +789,8 @@ static int watchdog_open(struct inode *i * If the /dev/watchdog device is open, we don't want the module * to be unloaded. */ - if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) { + hw_running = watchdog_hw_running(wdd); + if (!hw_running && !try_module_get(wdd->ops->owner)) { err = -EBUSY; goto out_clear; } @@ -799,7 +801,7 @@ static int watchdog_open(struct inode *i file->private_data = wd_data; - if (!watchdog_hw_running(wdd)) + if (!hw_running) kref_get(&wd_data->kref); /* dev/watchdog is a virtual (and thus non-seekable) filesystem */