From d1ed3ba4e3d76b4ebec239c64f990c26d7935700 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Tue, 8 Mar 2016 18:46:13 -0800 Subject: [PATCH] watchdog: Ensure that wdd is not dereferenced if NULL Smatch rightfully complains that wdd is dereferenced in the watchdog release function after being checked for NULL. Also make sure that it is not accessed outside mutex protection to avoid use-after-free problems. Fixes: e6c71e84e4c0 ("watchdog: Introduce WDOG_HW_RUNNING flag") Reported-by: Dan Carpenter Signed-off-by: Guenter Roeck Signed-off-by: Wim Van Sebroeck --- drivers/watchdog/watchdog_dev.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index 2d6110278eac..e2c5abbb45ff 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -711,6 +711,7 @@ static int watchdog_release(struct inode *inode, struct file *file) struct watchdog_core_data *wd_data = file->private_data; struct watchdog_device *wdd; int err = -EBUSY; + bool running; mutex_lock(&wd_data->lock); @@ -742,14 +743,15 @@ static int watchdog_release(struct inode *inode, struct file *file) clear_bit(_WDOG_DEV_OPEN, &wd_data->status); done: + running = wdd && watchdog_hw_running(wdd); mutex_unlock(&wd_data->lock); /* * Allow the owner module to be unloaded again unless the watchdog * is still running. If the watchdog is still running, it can not * be stopped, and its driver must not be unloaded. */ - if (!watchdog_hw_running(wdd)) { - module_put(wdd->ops->owner); + if (!running) { + module_put(wd_data->cdev.owner); kref_put(&wd_data->kref, watchdog_core_data_release); } return 0; -- 2.20.1