Re: [PATCH v5 05/18] watchdog: cpwd: use generic compat_ptr_ioctl

From: Guenter Roeck <linux@roeck-us.net>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk,
	linux-fsdevel@vger.kernel.org,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	linux-watchdog@vger.kernel.org
Subject: Re: [PATCH v5 05/18] watchdog: cpwd: use generic compat_ptr_ioctl
Date: Mon, 7 Oct 2019 16:28:32 -0700	[thread overview]
Message-ID: <20191007232832.GA26929@roeck-us.net> (raw)
In-Reply-To: <20190814204259.120942-6-arnd@arndb.de>

Arnd,

On Wed, Aug 14, 2019 at 10:42:32PM +0200, Arnd Bergmann wrote:
> The cpwd_compat_ioctl() contains a bogus mutex that dates
> back to a leftover BKL instance.
> 
> Simplify the implementation by using the new compat_ptr_ioctl()
> helper function that will do the right thing for all calls
> here.
> 
> Note that WIOCSTART/WIOCSTOP don't take any arguments, so
> the compat_ptr() conversion is not needed here, but it also
> doesn't hurt.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Reviewed-by: Guenter Roeck <linux@roeck-us.net>

This patch made it into the kernel, but the infrastructure didn't make it.
Do we need to revert it ?

Guenter

> ---
>  drivers/watchdog/cpwd.c | 25 +------------------------
>  1 file changed, 1 insertion(+), 24 deletions(-)
> 
> diff --git a/drivers/watchdog/cpwd.c b/drivers/watchdog/cpwd.c
> index b973b31179df..9393be584e72 100644
> --- a/drivers/watchdog/cpwd.c
> +++ b/drivers/watchdog/cpwd.c
> @@ -473,29 +473,6 @@ static long cpwd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	return 0;
>  }
>  
> -static long cpwd_compat_ioctl(struct file *file, unsigned int cmd,
> -			      unsigned long arg)
> -{
> -	int rval = -ENOIOCTLCMD;
> -
> -	switch (cmd) {
> -	/* solaris ioctls are specific to this driver */
> -	case WIOCSTART:
> -	case WIOCSTOP:
> -	case WIOCGSTAT:
> -		mutex_lock(&cpwd_mutex);
> -		rval = cpwd_ioctl(file, cmd, arg);
> -		mutex_unlock(&cpwd_mutex);
> -		break;
> -
> -	/* everything else is handled by the generic compat layer */
> -	default:
> -		break;
> -	}
> -
> -	return rval;
> -}
> -
>  static ssize_t cpwd_write(struct file *file, const char __user *buf,
>  			  size_t count, loff_t *ppos)
>  {
> @@ -520,7 +497,7 @@ static ssize_t cpwd_read(struct file *file, char __user *buffer,
>  static const struct file_operations cpwd_fops = {
>  	.owner =		THIS_MODULE,
>  	.unlocked_ioctl =	cpwd_ioctl,
> -	.compat_ioctl =		cpwd_compat_ioctl,
> +	.compat_ioctl =		compat_ptr_ioctl,
>  	.open =			cpwd_open,
>  	.write =		cpwd_write,
>  	.read =			cpwd_read,