Re: [PATCH] drm/core: Fix ordering in drm_mode_config_cleanup.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Mar 22, 2016 at 03:42:14PM +0100, Maarten Lankhorst wrote:
> __drm_atomic_helper_plane_destroy_state calls
> drm_framebuffer_unreference, which means that if drm_framebuffer_free
> is called before plane->destroy freed memory will be accessed.
> 
> A similar case happens for the blob list, which was freed before the
> crtc state was, resulting in the unreference_blob from crtc_destroy_state
> pointing to garbage memory causing another opportunity for a GPF.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_crtc.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 51c5a00ffdff..5a13b1afccbe 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -5958,6 +5958,15 @@ void drm_mode_config_cleanup(struct drm_device *dev)
>  		drm_property_destroy(dev, property);
>  	}

And what about props? Any chance of explosion due to those being gone?

>  
> +	list_for_each_entry_safe(plane, plt, &dev->mode_config.plane_list,
> +				 head) {
> +		plane->funcs->destroy(plane);
> +	}
> +
> +	list_for_each_entry_safe(crtc, ct, &dev->mode_config.crtc_list, head) {
> +		crtc->funcs->destroy(crtc);
> +	}
> +
>  	list_for_each_entry_safe(blob, bt, &dev->mode_config.property_blob_list,
>  				 head_global) {
>  		drm_property_unreference_blob(blob);
> @@ -5976,15 +5985,6 @@ void drm_mode_config_cleanup(struct drm_device *dev)
>  		drm_framebuffer_free(&fb->refcount);
>  	}
>  
> -	list_for_each_entry_safe(plane, plt, &dev->mode_config.plane_list,
> -				 head) {
> -		plane->funcs->destroy(plane);
> -	}
> -
> -	list_for_each_entry_safe(crtc, ct, &dev->mode_config.crtc_list, head) {
> -		crtc->funcs->destroy(crtc);
> -	}
> -
>  	ida_destroy(&dev->mode_config.connector_ida);
>  	idr_destroy(&dev->mode_config.tile_idr);
>  	idr_destroy(&dev->mode_config.crtc_idr);
> -- 
> 2.1.0
> 
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-- 
Ville Syrjälä
Intel OTC
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