Re: [PATCH] vt: Grab console_lock around con_is_bound in show_bind

[Daniel Vetter]

Hi Greg,

Do you plan to pick this up in your console/vt/whatever-fixes branch?
There's no reason for me to route this through drm-fixes.
-Daniel

On Thu, Jul 18, 2019 at 10:09:03AM +0200, Daniel Vetter wrote:
> Not really harmful not to, but also not harm in grabbing the lock. And
> this shuts up a new WARNING I introduced in commit ddde3c18b700 ("vt:
> More locking checks").
> 
> Reported-by: Jens Remus <jremus@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: linux-fbdev@xxxxxxxxxxxxxxx
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
> Cc: Martin Hostettler <textshell@xxxxxxxxxxx>
> Cc: Adam Borowski <kilobyte@xxxxxxxxxx>
> Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> ---
>  drivers/tty/vt/vt.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index ec92f36ab5c4..34aa39d1aed9 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -3771,7 +3771,11 @@ static ssize_t show_bind(struct device *dev, struct device_attribute *attr,
>  			 char *buf)
>  {
>  	struct con_driver *con = dev_get_drvdata(dev);
> -	int bind = con_is_bound(con->con);
> +	int bind;
> +
> +	console_lock();
> +	bind = con_is_bound(con->con);
> +	console_unlock();
>  
>  	return snprintf(buf, PAGE_SIZE, "%i\n", bind);
>  }
> -- 
> 2.20.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch