linux-kernel - Re: [PATCH 1/2] watchdog: menz069_wdt: fix watchdog initialisation

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Message-ID: <ed83c3a3-1189-3d8d-08b5-014bcfce88cc@roeck-us.net>
Date:   Tue, 18 Apr 2023 11:20:54 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Johannes Thumshirn <jth@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] watchdog: menz069_wdt: fix watchdog initialisation

On 4/18/23 10:25, Johannes Thumshirn wrote:
> Doing a 'cat /dev/watchdog0' with menz069_wdt as watchdog0 will result in
> a NULL pointer dereference.
> 
> This happens because we're passing the wrong pointer to
> watchdog_register_device(). Fix this by getting rid of the static
> watchdog_device structure and use the one embedded into the driver's
> per-instance private data.
> 
> Signed-off-by: Johannes Thumshirn <jth@...nel.org>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/menz69_wdt.c | 16 ++++++----------
>   1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/watchdog/menz69_wdt.c b/drivers/watchdog/menz69_wdt.c
> index 8973f98bc6a5..bca0938f3429 100644
> --- a/drivers/watchdog/menz69_wdt.c
> +++ b/drivers/watchdog/menz69_wdt.c
> @@ -98,14 +98,6 @@ static const struct watchdog_ops men_z069_ops = {
>   	.set_timeout = men_z069_wdt_set_timeout,
>   };
>   
> -static struct watchdog_device men_z069_wdt = {
> -	.info = &men_z069_info,
> -	.ops = &men_z069_ops,
> -	.timeout = MEN_Z069_DEFAULT_TIMEOUT,
> -	.min_timeout = 1,
> -	.max_timeout = MEN_Z069_WDT_COUNTER_MAX / MEN_Z069_TIMER_FREQ,
> -};
> -
>   static int men_z069_probe(struct mcb_device *dev,
>   			  const struct mcb_device_id *id)
>   {
> @@ -125,15 +117,19 @@ static int men_z069_probe(struct mcb_device *dev,
>   		goto release_mem;
>   
>   	drv->mem = mem;
> +	drv->wdt.info = &men_z069_info;
> +	drv->wdt.ops = &men_z069_ops;
> +	drv->wdt.timeout = MEN_Z069_DEFAULT_TIMEOUT;
> +	drv->wdt.min_timeout = 1;
> +	drv->wdt.max_timeout = MEN_Z069_WDT_COUNTER_MAX / MEN_Z069_TIMER_FREQ;
>   
> -	drv->wdt = men_z069_wdt;
>   	watchdog_init_timeout(&drv->wdt, 0, &dev->dev);
>   	watchdog_set_nowayout(&drv->wdt, nowayout);
>   	watchdog_set_drvdata(&drv->wdt, drv);
>   	drv->wdt.parent = &dev->dev;
>   	mcb_set_drvdata(dev, drv);
>   
> -	return watchdog_register_device(&men_z069_wdt);
> +	return watchdog_register_device(&drv->wdt);
>   
>   release_mem:
>   	mcb_release_mem(mem);