diff options
| author | Guenter Roeck <linux@roeck-us.net> | 2017-09-25 09:17:01 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-24 11:01:23 +0100 |
| commit | 08b81090102015fb88572dda91934aab0de88893 (patch) | |
| tree | 41ab15e7342affab1c0cb712bf24edb1c649938d /drivers/watchdog | |
| parent | 008029510ac8c44a8421180d8d71b3e9c95c909f (diff) | |
watchdog: Fix potential kref imbalance when opening watchdog
[ 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 <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>
Diffstat (limited to 'drivers/watchdog')
| -rw-r--r-- | drivers/watchdog/watchdog_dev.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index 0826e663bd5a..e6edf3737ea7 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -768,6 +768,7 @@ static int watchdog_open(struct inode *inode, struct file *file) { struct watchdog_core_data *wd_data; struct watchdog_device *wdd; + bool hw_running; int err; /* Get the corresponding watchdog device */ @@ -787,7 +788,8 @@ static int watchdog_open(struct inode *inode, struct file *file) * 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; } @@ -798,7 +800,7 @@ static int watchdog_open(struct inode *inode, struct file *file) 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 */ |