Hello Krzysztof,
On 16/07/2020 13:32, krzysztof.sobota@xxxxxxxxx wrote:
> When watchdog device is being registered, it calls misc_register that
> makes watchdog available for systemd to open. This is a data race
> scenario, because when device is open it may still have device struct
> not initialized - this in turn causes a crash. This patch moves
> device initialization before misc_register call and it solves the
> problem printed below.
[...]
thank you for looking into this!
> Fixes: 72139dfa2464 ("watchdog: Fix the race between the release of watchdog_core_data and cdev")
> Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> Signed-off-by: Krzysztof Sobota <krzysztof.sobota@xxxxxxxxx>
> ---
> v1 -> v2:
> * removed Change-Id tag
> * added Review-by tag
> v2 -> v3
> * convert spaces to tabs
> * convert (hopefully) mail to plaintext
> ---
> drivers/watchdog/watchdog_dev.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index 10b2090f3e5e..1c322caecf7f 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -947,6 +947,15 @@ static int watchdog_cdev_register(struct watchdog_device *wdd)
> if (IS_ERR_OR_NULL(watchdog_kworker))
> return -ENODEV;
>
> + device_initialize(&wd_data->dev);
> + wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
> + wd_data->dev.class = &watchdog_class;
> + wd_data->dev.parent = wdd->parent;
> + wd_data->dev.groups = wdd->groups;
> + wd_data->dev.release = watchdog_core_data_release;
> + dev_set_drvdata(&wd_data->dev, wdd);
> + dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
> +
> kthread_init_work(&wd_data->work, watchdog_ping_work);
> hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> wd_data->timer.function = watchdog_timer_expired;
> @@ -967,15 +976,6 @@ static int watchdog_cdev_register(struct watchdog_device *wdd)
> }
> }
>
> - device_initialize(&wd_data->dev);
> - wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
> - wd_data->dev.class = &watchdog_class;
> - wd_data->dev.parent = wdd->parent;
> - wd_data->dev.groups = wdd->groups;
> - wd_data->dev.release = watchdog_core_data_release;
> - dev_set_drvdata(&wd_data->dev, wdd);
> - dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
> -
> /* Fill in the data structures */
> cdev_init(&wd_data->cdev, &watchdog_fops);
>
> --
> 2.14.0
>
--
Best regards,
Alexander Sverdlin.
