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=-11.2 required=3.0 tests=BAYES_00,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_SANE_1 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 7D570C5517A for ; Tue, 10 Nov 2020 16:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 141BE206E3 for ; Tue, 10 Nov 2020 16:01:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Fg5+setH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731244AbgKJQBY (ORCPT ); Tue, 10 Nov 2020 11:01:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729909AbgKJQBV (ORCPT ); Tue, 10 Nov 2020 11:01:21 -0500 Received: from mail-oi1-x241.google.com (mail-oi1-x241.google.com [IPv6:2607:f8b0:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6959C0613CF; Tue, 10 Nov 2020 08:01:21 -0800 (PST) Received: by mail-oi1-x241.google.com with SMTP id j7so14865826oie.12; Tue, 10 Nov 2020 08:01:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=kDzPapGdXIwmXcJmTQZGIuILt4q/vwSqlKWbIudkGQY=; b=Fg5+setHdx6WcyATDh9i9QQsjuOKojB/1HwsGCqR109+KSbAOS3mznvx0Zmn+VViOH j8y3HTl4hsgjbcXiWmz56YdPS+uvtgUeEjzvAGciQd+uEmR/I4C/hfvY4ttxZ7gny16y tkM93eZBRudiBqKZ6vQMAUSV84S6DrKKpiz8sHeptHCbjmkc8R34MmuyAZwme6iupq9j 410RZ+rSPuBFSJLUli3WB4Tlgfu554FOgAg9UjyeMecGI0M2XQLlJEPTQlya9CEhHmwS Z3fgkTQXE63ONPBfjW8t0/OTjBiQJb6wk3AyitVH9Aezn6SyRDdrYCOqQAJz+2Rbynrw 3Ktg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=kDzPapGdXIwmXcJmTQZGIuILt4q/vwSqlKWbIudkGQY=; b=ZoPVJd8IbvPF6PkUcu+NNXySi5cByiP3QWNHEmGupEEKGF3T+gkEmj/OWfuxosnYNT H3zKOHLn4DgAeKcwpPNdkM0lbnDqD4r/44+jwuGzrUr0a20ExetcMcevX5gbhrSyAK5t /eQeUcc5fuxu1gvqUxflZLr9+M14Z3drX9mm1/5H9nYV0uHkZbKx4mUwLAZgTcbFgu/J Yxlg5y2ShzZGlSmy96vGJIigW8GA4iEhbUq6D1LakQln1Rgt7MbLAtrym34FwDxXouO/ hKCJnDOcYCDoIXrIxK/rl2oduOIu3fyaK29rykssHtH0NSJGCM1A6x44JkweCPht6T+j DAxA== X-Gm-Message-State: AOAM533NuL987SriT/3gZQHK2rIZKi4mAFUaZAmri6Vit+JFBWb+J43Y VyGE+gVRD2/qp2Iyh3whPKPH4o4pF6k= X-Google-Smtp-Source: ABdhPJwCXuNKmg2h/odhEd9J6ZKMR6oT6qD8+oU+Elb6I9ADZ62BM2n0Y/GvGA1TUOO+UqOucAuKYw== X-Received: by 2002:aca:b288:: with SMTP id b130mr3031391oif.152.1605024080787; Tue, 10 Nov 2020 08:01:20 -0800 (PST) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id t6sm3231782ooo.22.2020.11.10.08.01.19 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 10 Nov 2020 08:01:19 -0800 (PST) Sender: Guenter Roeck Date: Tue, 10 Nov 2020 08:01:18 -0800 From: Guenter Roeck To: Wang Wensheng Cc: wim@linux-watchdog.org, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org, rui.xiang@huawei.com Subject: Re: [PATCH -next v4] watchdog: Fix potential dereferencing of null pointer Message-ID: <20201110160118.GA17288@roeck-us.net> References: <20201109130512.28121-1-wangwensheng4@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201109130512.28121-1-wangwensheng4@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 09, 2020 at 01:05:12PM +0000, Wang Wensheng wrote: > A reboot notifier, which stops the WDT by calling the stop hook without > any check, would be registered when we set WDOG_STOP_ON_REBOOT flag. > > Howerer we allow the WDT driver to omit the stop hook since commit > "d0684c8a93549" ("watchdog: Make stop function optional") and provide > a module parameter for user that controls the WDOG_STOP_ON_REBOOT flag > in commit 9232c80659e94 ("watchdog: Add stop_on_reboot parameter to > control reboot policy"). Together that commits make user potential to > insert a watchdog driver that don't provide a stop hook but with the > stop_on_reboot parameter set, then dereferencing of null pointer occurs > on system reboot. > > Check the stop hook before registering the reboot notifier to fix the > issue. > > Fixes: d0684c8a9354 ("watchdog: Make stop function optional") > Signed-off-by: Wang Wensheng Reviewed-by: Guenter Roeck > --- > drivers/watchdog/watchdog_core.c | 22 +++++++++++++--------- > 1 file changed, 13 insertions(+), 9 deletions(-) > > diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c > index 423844757812..0e9a99559609 100644 > --- a/drivers/watchdog/watchdog_core.c > +++ b/drivers/watchdog/watchdog_core.c > @@ -267,15 +267,19 @@ static int __watchdog_register_device(struct watchdog_device *wdd) > } > > if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { > - wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; > - > - ret = register_reboot_notifier(&wdd->reboot_nb); > - if (ret) { > - pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", > - wdd->id, ret); > - watchdog_dev_unregister(wdd); > - ida_simple_remove(&watchdog_ida, id); > - return ret; > + if (!wdd->ops->stop) > + pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id); > + else { > + wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; > + > + ret = register_reboot_notifier(&wdd->reboot_nb); > + if (ret) { > + pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", > + wdd->id, ret); > + watchdog_dev_unregister(wdd); > + ida_simple_remove(&watchdog_ida, id); > + return ret; > + } > } > } > > -- > 2.25.0 >