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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>
hifive-unleashed-5.1
Hans de Goede 2012-05-22 11:40:27 +02:00 committed by Wim Van Sebroeck
parent 85a2e40cb5
commit 54e2dc9341
1 changed files with 29 additions and 1 deletions
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30
drivers/hwmon/sch56xx-common.c
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@ -67,6 +67,7 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
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 @@ EXPORT_SYMBOL(sch56xx_read_virtual_reg12);
* 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 @@ static int watchdog_stop(struct watchdog_device *wddev)
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 @@ struct sch56xx_watchdog_data *sch56xx_watchdog_register(struct device *parent,
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 @@ EXPORT_SYMBOL(sch56xx_watchdog_register);
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);