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

[Rob Clark]

On Fri, Oct 16, 2015 at 12:23 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> In
>
> commit bbb1e52402b2a288b09ae37e8182599931c7e9df
> Author: Rob Clark <robdclark at 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.

oh, whoops

> OCD-align function parameters while at it.

did you mean to drop that line from the commit msg, or include an
extra hunk that you missed?

at any rate,

Reviewed-by: Rob Clark <robdclark at gmail.com>

> Cc: Rob Clark <robdclark at gmail.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at gmail.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92483
> Signed-off-by: Daniel Vetter <daniel.vetter at 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:
> +       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
>