Re: [PATCH 2/2] drm/fb-helper: Fix fb refcounting in pan_display_atomic

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

On Fri, Oct 16, 2015 at 06:23:14PM +0200, Daniel Vetter wrote:
> In
> 
> commit bbb1e52402b2a288b09ae37e8182599931c7e9df
> Author: Rob Clark <robdclark@gmail.com>
> Date:   Tue Aug 25 15:35:58 2015 -0400
> 
>     drm/fb-helper: atomic restore_fbdev_mode()..
> 
> we've forgotten to do the plane->old_fb refcount dance for
> pan_display_atomic, which can result in refcount leaks if the current
> configuration is not from fbcon. Which apparently can happen when
> vt-switching - fbcon does a pan first before a set_par.
> 
> OCD-align function parameters while at it.
> 
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92483
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 0ac0fcc9b0d2..b2cf28dd90fe 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1249,6 +1249,8 @@ retry:
>  
>  		mode_set = &fb_helper->crtc_info[i].mode_set;
>  
> +		mode_set->crtc->primary->old_fb = mode_set->crtc->primary->fb;
> +
>  		mode_set->x = var->xoffset;
>  		mode_set->y = var->yoffset;
>  
> @@ -1264,13 +1266,34 @@ retry:
>  	info->var.xoffset = var->xoffset;
>  	info->var.yoffset = var->yoffset;
>  
> -	return 0;
>  
>  fail:

Time to rename the label too?

> +	for(i = 0; i < fb_helper->crtc_count; i++) {
> +		struct drm_mode_set *mode_set;
> +		struct drm_plane *plane;
> +
> +		mode_set = &fb_helper->crtc_info[i].mode_set;
> +		plane = mode_set->crtc->primary;
> +
> +		if (ret == 0) {
> +			struct drm_framebuffer *new_fb = plane->state->fb;
> +
> +			if (new_fb)
> +				drm_framebuffer_reference(new_fb);
> +			plane->fb = new_fb;
> +			plane->crtc = plane->state->crtc;
> +
> +			if (plane->old_fb)
> +				drm_framebuffer_unreference(plane->old_fb);
> +		}
> +		plane->old_fb = NULL;
> +	}
> +
>  	if (ret == -EDEADLK)
>  		goto backoff;
>  
> -	drm_atomic_state_free(state);
> +	if (ret != 0)
> +		drm_atomic_state_free(state);
>  
>  	return ret;
>  
> -- 
> 2.5.1
> 
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-- 
Ville Syrjälä
Intel OTC
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