From patchwork Mon Nov 9 13:05:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wang Wensheng X-Patchwork-Id: 321900 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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,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 EC50EC4741F for ; Mon, 9 Nov 2020 13:34:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ADFF4206ED for ; Mon, 9 Nov 2020 13:34:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730932AbgKINee (ORCPT ); Mon, 9 Nov 2020 08:34:34 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:7068 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730913AbgKINFp (ORCPT ); Mon, 9 Nov 2020 08:05:45 -0500 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4CVB7H0z5XzhXkr; Mon, 9 Nov 2020 21:05:31 +0800 (CST) Received: from huawei.com (10.175.112.208) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.487.0; Mon, 9 Nov 2020 21:05:32 +0800 From: Wang Wensheng To: , , , CC: Subject: [PATCH -next v4] watchdog: Fix potential dereferencing of null pointer Date: Mon, 9 Nov 2020 13:05:12 +0000 Message-ID: <20201109130512.28121-1-wangwensheng4@huawei.com> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 X-Originating-IP: [10.175.112.208] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org 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; + } } }