[PATCH] drm: udl: Destroy framebuffer only if it was initialized

[Sean Paul]

On Fri, Apr 20, 2018 at 01:50:01PM +0200, Emil Lundmark wrote:
> This fixes a NULL pointer dereference that can happen if the UDL
> driver is unloaded before the framebuffer is initialized. This can
> happen e.g. if the USB device is unplugged right after it was plugged
> in.
> 

JFYI, in future, if someone makes a suggestion on how to fix a bug, it's good
practice to add a Suggested-by tag to give credit.

Reviewed-by: Sean Paul <seanpaul at chromium.org>

> Signed-off-by: Emil Lundmark <lndmrk at chromium.org>
> ---
>  drivers/gpu/drm/udl/udl_fb.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
> index 2ebdc6d5a76e..5754e37f741b 100644
> --- a/drivers/gpu/drm/udl/udl_fb.c
> +++ b/drivers/gpu/drm/udl/udl_fb.c
> @@ -426,9 +426,11 @@ static void udl_fbdev_destroy(struct drm_device *dev,
>  {
>  	drm_fb_helper_unregister_fbi(&ufbdev->helper);
>  	drm_fb_helper_fini(&ufbdev->helper);
> -	drm_framebuffer_unregister_private(&ufbdev->ufb.base);
> -	drm_framebuffer_cleanup(&ufbdev->ufb.base);
> -	drm_gem_object_put_unlocked(&ufbdev->ufb.obj->base);
> +	if (ufbdev->ufb.obj) {
> +		drm_framebuffer_unregister_private(&ufbdev->ufb.base);
> +		drm_framebuffer_cleanup(&ufbdev->ufb.base);
> +		drm_gem_object_put_unlocked(&ufbdev->ufb.obj->base);
> +	}
>  }
>  
>  int udl_fbdev_init(struct drm_device *dev)
> -- 
> 2.17.0.484.g0c8726318c-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS