watchdog: Ensure that wdd is not dereferenced if NULL

PATCH New Guenter Roeck 1 participant 1 message Mar 9, 2016 Watchdog device drivers

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Guenter Roeck

author maintainer

2016-03-09 02:46 UTC #0 lore raw

PATCH 1/1 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 <[email protected]>

Signed-off-by Guenter Roeck <[email protected]>

---
Wim,

please feel free to merge with the original commit if your prefer.

Thanks,
Guenter

 drivers/watchdog/watchdog_dev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

drivers/watchdog/watchdog_dev.c +4 -2

index 2d6110278eac..e2c5abbb45ff 100644
@@ -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;

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2.5.0