watchdog: sch56xx-common: Add proper ref-counting of watchdog data
This fixes referencing free-ed memory in the corner case where /dev/watchdog
is open when the platform driver gets unbound from the platform device.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/drivers/hwmon/sch56xx-common.c b/drivers/hwmon/sch56xx-common.c
index 35846cb..839087c 100644
--- a/drivers/hwmon/sch56xx-common.c
+++ b/drivers/hwmon/sch56xx-common.c
@@ -67,6 +67,7 @@
struct sch56xx_watchdog_data {
u16 addr;
struct mutex *io_lock;
+ struct kref kref;
struct watchdog_info wdinfo;
struct watchdog_device wddev;
u8 watchdog_preset;
@@ -257,6 +258,15 @@
* Watchdog routines
*/
+/* Release our data struct when we're unregistered *and*
+ all references to our watchdog device are released */
+static void watchdog_release_resources(struct kref *r)
+{
+ struct sch56xx_watchdog_data *data =
+ container_of(r, struct sch56xx_watchdog_data, kref);
+ kfree(data);
+}
+
static int watchdog_set_timeout(struct watchdog_device *wddev,
unsigned int timeout)
{
@@ -385,12 +395,28 @@
return 0;
}
+static void watchdog_ref(struct watchdog_device *wddev)
+{
+ struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
+
+ kref_get(&data->kref);
+}
+
+static void watchdog_unref(struct watchdog_device *wddev)
+{
+ struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
+
+ kref_put(&data->kref, watchdog_release_resources);
+}
+
static const struct watchdog_ops watchdog_ops = {
.owner = THIS_MODULE,
.start = watchdog_start,
.stop = watchdog_stop,
.ping = watchdog_trigger,
.set_timeout = watchdog_set_timeout,
+ .ref = watchdog_ref,
+ .unref = watchdog_unref,
};
struct sch56xx_watchdog_data *sch56xx_watchdog_register(struct device *parent,
@@ -422,6 +448,7 @@
data->addr = addr;
data->io_lock = io_lock;
+ kref_init(&data->kref);
strlcpy(data->wdinfo.identity, "sch56xx watchdog",
sizeof(data->wdinfo.identity));
@@ -467,7 +494,8 @@
void sch56xx_watchdog_unregister(struct sch56xx_watchdog_data *data)
{
watchdog_unregister_device(&data->wddev);
- kfree(data);
+ kref_put(&data->kref, watchdog_release_resources);
+ /* Don't touch data after this it may have been free-ed! */
}
EXPORT_SYMBOL(sch56xx_watchdog_unregister);