linux-kernel - Re: [PATCH for-4.5] watchdog/rc32434

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Date:	Sun, 28 Feb 2016 07:56:55 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	stable@...r.kernel.org, Wim Van Sebroeck <wim@...ana.be>,
	linux-watchdog@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH for-4.5] watchdog/rc32434_wdt: fix ioctl error handling

On 02/28/2016 07:44 AM, Michael S. Tsirkin wrote:
> Calling return copy_to_user(...) in an ioctl will not do the right thing
> if there's a pagefault: copy_to_user returns the number of bytes not
> copied in this case.
>
> Fix up watchdog/rc32434_wdt to do
> 	return copy_to_user(...)) ?  -EFAULT : 0;
>
> instead.
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

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

> ---
>
> Untested.
>
>   drivers/watchdog/rc32434_wdt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/watchdog/rc32434_wdt.c b/drivers/watchdog/rc32434_wdt.c
> index 71e78ef..3a75f3b 100644
> --- a/drivers/watchdog/rc32434_wdt.c
> +++ b/drivers/watchdog/rc32434_wdt.c
> @@ -237,7 +237,7 @@ static long rc32434_wdt_ioctl(struct file *file, unsigned int cmd,
>   			return -EINVAL;
>   		/* Fall through */
>   	case WDIOC_GETTIMEOUT:
> -		return copy_to_user(argp, &timeout, sizeof(int));
> +		return copy_to_user(argp, &timeout, sizeof(int)) ? -EFAULT : 0;
>   	default:
>   		return -ENOTTY;
>   	}
>