[PATCH] drm/fb-helper: Fix a potential NULL dereference

[Daniel Vetter]

On Wed, Dec 06, 2017 at 04:07:49PM +0300, Dan Carpenter wrote:
> We recently modified drm_fb_helper_single_add_all_connectors() to allow
> NULL "fb_helper" pointers.  But  the problem is that it gets
> dereferenced before we checked for NULL.
> 
> Fixes: c777990fb45b ("drm/fb-helper: Handle function NULL argument")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

Just merged a similar patch yesterday (drat yours slightly prettier!):

commit 89f3f35620c7f244880485de11079cb4d98ed604 (HEAD -> drm-misc-next, drm-misc/for-linux-next, drm-misc/drm-misc-next)
Author: Gustavo A. R. Silva <garsilva at embeddedor.com>
Date:   Tue Dec 5 11:46:28 2017 -0600

    drm/fb-helper: Fix potential NULL pointer dereference

Thanks anyway,
-Daniel
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 6654f2f87775..f73457e5bbbc 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -178,7 +178,6 @@ EXPORT_SYMBOL(drm_fb_helper_add_one_connector);
>   */
>  int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
>  {
> -	struct drm_device *dev = fb_helper->dev;
>  	struct drm_connector *connector;
>  	struct drm_connector_list_iter conn_iter;
>  	int i, ret = 0;
> @@ -187,7 +186,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
>  		return 0;
>  
>  	mutex_lock(&fb_helper->lock);
> -	drm_connector_list_iter_begin(dev, &conn_iter);
> +	drm_connector_list_iter_begin(fb_helper->dev, &conn_iter);
>  	drm_for_each_connector_iter(connector, &conn_iter) {
>  		ret = __drm_fb_helper_add_one_connector(fb_helper, connector);
>  		if (ret)
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch