From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pz2-f39.google.com (mail-pz2-f39.google.com [74.125.228.39]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B9B2552CCF0 for ; Tue, 29 Sep 2026 13:46:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.228.39 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790689603; cv=none; b=ou2auoPZiYXgz8BFtUDqju6TRBUok5Fc6ZGp/B4AOg/TLhA7t+SZvvBqb+38TnoBTb9JjFt2K9ObP6tHNkF/qW7Rg0vrtFgBmLlJvJEKOc67rcEyEIK5rfJljw9gFS1YSupneOyQaYNT2V7sO1Y6TY+8dmtmPIJpiGe8ivREc2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790689603; c=relaxed/simple; bh=wpDlTr/QWpQupJUNMM2wALQN8Uyz1bY9/O7nko4Cg6E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DpWFqUcTLY7GpyRJCju8khu2xqRYxpU6xchewzDQxPJjvnHDrEGjOXSdPWjI3DQw7CTCO5FcNGUQUf5s5iWpXq0pQJbto3NuyP6RpSAlS92B2pYZyDkxq8D1/2zcyIz3cg56Yi3lEUIEDCZjgAdAqcnvGe61Jc5pqvufm2d9BpM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=dpWjgzRJ; arc=none smtp.client-ip=74.125.228.39 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dpWjgzRJ" Received: by mail-pz2-f39.google.com with SMTP id 41be03b00d2f7-cc7901f7971so1335824a12.0 for ; Tue, 29 Sep 2026 06:46:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790689601; x=1791294401; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:from:to:cc:subject:date :message-id:reply-to:content-type; bh=MNjMUkShSGX1g13GJX2GC8qsPlf5nslC/UppE0cymdg=; b=dpWjgzRJxWBt25CJ7MDPmv2EvOZlGpzhiW50HMsLTZYvPvqPTCVZ3wEFbqVH4Kxn8a BYq4vLqUtb81tSz4TncWVHSo5xjUdLYsJUlvYdjCjk00lfkxHel4x5yQfuE0x0ed+DRJ y8jg4hjtXbg0R1Rfa62Eymh78kRibVpZC+MwMweg7i0IA7hTn/MeNADYmUYRcXfbS54Q w4dG0Y0jzhkOQZX531X7XaYgPZSJ/Vv4NRbEVWkigWKiJUgdwOSgOjaBWcC/2AAoj/cA en6/laIpx+LFpYZqeVx6ySNWcQSoA+diqAi5Iop9YRT4gBclUu8wqBHO0pevWIjzy/AN geXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790689601; x=1791294401; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=MNjMUkShSGX1g13GJX2GC8qsPlf5nslC/UppE0cymdg=; b=KP+Ltg30somdoZdx+pl7xUDl4Px93aaZUPgfgNqy0gN2TidI+5nofWCIrJosHbCNBP 1MzUSa6gLaphDwGl+IwITMRMCpRp38hwiPXIlBoT0UZrx3hXT77bDtWwzkk3J1cZPKrq 0HHflrna6ZARcbG9v/uYiDyWMOQd0jOt0ATU8Rswrj6p7YkeWO8po5d2qyp2gJr/bwfQ YPHKmq/+OlYO2ckVVJfflFISf+Nqxco2REZWonfW/Z9yJQqdP4Ufc0RKIQu50mIXkFF0 Q4Xrgl55aVUPrsnLpSWbp6oykigLTOme0DGU9E6+G6l6NUZnQJ/EJ0Qid7XCDwbMjOZW WU3A== X-Gm-Message-State: AFuF++nEpXndMDdZES+Bct+PD8Bm5r4J58vpOfFKDR+iZwVz26sqnfOc fAQKbPcR/ohgnpgn3ef9xB8C1qOr4BKYmsk8u1nWUK0y/o3d9tSJ2DbgXOKj6EsH X-Gm-Gg: AYBFou24aZ1qYZhVNX7RgymepH4z4WUJ9GqrPAaIz19gDqTobS+CjD60OZw1P36ZOZd ybgYZqb068sbNLSO1Quf89V2PqX3UN9gAeIzpMa7CIOGpqsH1y+WrtmWhiiyyubqCl/KZ66ndM7 u5cQTuHGZF7OHQEaUhYKrQn5eMw3/PsUs/XurIZ3sjRbD5bpV8ZiAL7KCun6viHXELosHNLT3IA Ft2bbwr77yuQka7ioqwwarjWqTV4lTUOx+PRY0Cc6BIy6uoigrbqBcgdWo2gF/X8t9UJ1I6orJj ZNxFYp6bWM+98hOyFImGVg+XP09kS2HI445lNWj0JlQOPLYzMMvN3s1/JO23vs+Jw9R1xxO14dv tbjwHSQplkadWlwTuRdCBX1/wkk52Rh4uhs8Fv/o+kNsL1qhIreHEC1cDadKbreblkfvhxv/yEN NhyrlG6dziL92BbJle1N2DtkiMwOENEtkHGxRZBUET6LZt39t1uAu7hOiCVy4lvYFXVoRUYDY1f ez7RIDpL0kh X-Received: by 2002:a05:6a21:3994:b0:3cd:8bba:824f with SMTP id adf61e73a8af0-3de0e70bc28mr13563549637.4.1790689601101; Tue, 29 Sep 2026 06:46:41 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc7cf5a2f74sm474872a12.10.2026.09.29.06.46.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2026 06:46:40 -0700 (PDT) Sender: Guenter Roeck From: Guenter Roeck To: linux-watchdog@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Guenter Roeck Subject: [PATCH 2/8] watchdog: core: Add missing locks Date: Tue, 29 Sep 2026 06:46:29 -0700 Message-ID: <20260929134635.2567137-3-linux@roeck-us.net> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20260929134635.2567137-1-linux@roeck-us.net> References: <20260929134635.2567137-1-linux@roeck-us.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add missing locks to watchdog_open(), watchdog_cdev_unregister(), and watchdog_set_last_hw_keepalive(). Also protect old_wd_data with its own lock to prevent its modification while in use, acquiring wd_data->lock before releasing old_wd_data_lock in watchdog_open() to avoid a TOCTOU race, and keeping misc_deregister() outside old_wd_data_lock to avoid lock ordering inversion with misc_mtx. Fixes: b4ffb1909843 ("watchdog: Separate and maintain variables based on variable lifetime") Assisted-by: LLM Signed-off-by: Guenter Roeck --- drivers/watchdog/watchdog_dev.c | 42 ++++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 6 deletions(-) diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index ed5b35184271..50224877ff49 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -55,6 +55,7 @@ static dev_t watchdog_devt; /* Reference to watchdog device behind /dev/watchdog */ static struct watchdog_core_data *old_wd_data; +static DEFINE_MUTEX(old_wd_data_lock); static struct kthread_worker *watchdog_kworker; @@ -869,17 +870,32 @@ static int watchdog_open(struct inode *inode, struct file *file) int err; /* Get the corresponding watchdog device */ - if (imajor(inode) == MISC_MAJOR) + if (imajor(inode) == MISC_MAJOR) { + mutex_lock(&old_wd_data_lock); wd_data = old_wd_data; - else + if (!wd_data) { + mutex_unlock(&old_wd_data_lock); + return -ENODEV; + } + mutex_lock(&wd_data->lock); + mutex_unlock(&old_wd_data_lock); + } else { wd_data = container_of(inode->i_cdev, struct watchdog_core_data, cdev); + mutex_lock(&wd_data->lock); + } /* the watchdog is single open! */ - if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status)) + if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status)) { + mutex_unlock(&wd_data->lock); return -EBUSY; + } wdd = wd_data->wdd; + if (!wdd) { + err = -ENODEV; + goto out_clear; + } /* * If the /dev/watchdog device is open, we don't want the module @@ -909,6 +925,8 @@ static int watchdog_open(struct inode *inode, struct file *file) */ wd_data->open_deadline = KTIME_MAX; + mutex_unlock(&wd_data->lock); + /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ return stream_open(inode, file); @@ -916,6 +934,7 @@ static int watchdog_open(struct inode *inode, struct file *file) module_put(wd_data->wdd->ops->owner); out_clear: clear_bit(_WDOG_DEV_OPEN, &wd_data->status); + mutex_unlock(&wd_data->lock); return err; } @@ -1085,7 +1104,9 @@ static int watchdog_cdev_register(struct watchdog_device *wdd) wdd->id, MAJOR(watchdog_devt), wdd->id); if (wdd->id == 0) { misc_deregister(&watchdog_miscdev); + mutex_lock(&old_wd_data_lock); old_wd_data = NULL; + mutex_unlock(&old_wd_data_lock); } mutex_lock(&wd_data->lock); wd_data->wdd = NULL; @@ -1131,9 +1152,12 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) cdev_device_del(&wd_data->cdev, &wd_data->dev); if (wdd->id == 0) { misc_deregister(&watchdog_miscdev); + mutex_lock(&old_wd_data_lock); old_wd_data = NULL; + mutex_unlock(&old_wd_data_lock); } + mutex_lock(&wd_data->lock); if (watchdog_active(wdd) && test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) { watchdog_stop(wdd); @@ -1141,7 +1165,6 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd) watchdog_hrtimer_pretimeout_stop(wdd); - mutex_lock(&wd_data->lock); wd_data->wdd = NULL; wdd->wd_data = NULL; mutex_unlock(&wd_data->lock); @@ -1208,20 +1231,27 @@ int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd, { struct watchdog_core_data *wd_data; ktime_t now; + int ret = 0; if (!wdd) return -EINVAL; wd_data = wdd->wd_data; + if (!wd_data) + return -ENODEV; + + mutex_lock(&wd_data->lock); now = ktime_get(); wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms)); if (watchdog_hw_running(wdd) && handle_boot_enabled) - return __watchdog_ping(wdd); + ret = __watchdog_ping(wdd); - return 0; + mutex_unlock(&wd_data->lock); + + return ret; } EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive); -- 2.45.2