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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Sebastian Reichel <sebastian.reichel@collabora.co.uk>,
        Guenter Roeck <linux@roeck-us.net>,
        Wim Van Sebroeck <wim@iguana.be>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.14 23/77] watchdog: Fix kref imbalance seen if handle_boot_enabled=0
Date:   Fri, 23 Mar 2018 10:53:57 +0100
Message-Id: <20180323094143.750833773@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@roeck-us.net>


[ Upstream commit 914d65f3f013ba2556c7beec5d3baac7b3292504 ]

If handle_boot_enabled is set to 0, the watchdog driver module use
counter will not be increased and kref_get() will not be called when
registering the watchdog. Subsequently, on open, this does not happen
either because the code believes that it was already done because the
hardware watchdog is marked as running.

We could introduce a state variable to indicate this state, but let's
just increase the module use counter and call kref_get() unconditionally
if the hardware watchdog is running when a driver is registering itself
to keep the code simple.

Fixes: 2501b015313fe ("watchdog: core: add option to avoid early ...")
Cc: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/watchdog/watchdog_dev.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -966,14 +966,13 @@ static int watchdog_cdev_register(struct
 	 * and schedule an immediate ping.
 	 */
 	if (watchdog_hw_running(wdd)) {
-		if (handle_boot_enabled) {
-			__module_get(wdd->ops->owner);
-			kref_get(&wd_data->kref);
+		__module_get(wdd->ops->owner);
+		kref_get(&wd_data->kref);
+		if (handle_boot_enabled)
 			queue_delayed_work(watchdog_wq, &wd_data->work, 0);
-		} else {
+		else
 			pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
-					wdd->id);
-		}
+				wdd->id);
 	}
 
 	return 0;