[RFC] drm/exynos: abort commit when framebuffer is removed from plane

[Rahul Sharma]

This situation arises when userspace remove the frambuffer object
and call setmode ioctl.

drm_mode_rmfb --> drm_plane_force_disable --> plane->crtc = NULL;
and
drm_mode_setcrtc --> exynos_plane_commit --> passes plane->crtc to
exynos_drm_crtc_plane_commit which is NULL.

This crashes the system.

Signed-off-by: Rahul Sharma <rahul.sharma at samsung.com>
---
This works fine but I am not confident on the correctness of the
solution.

 drivers/gpu/drm/exynos/exynos_drm_crtc.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c 
b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
index 95c9435..da4efe4 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
@@ -165,6 +165,12 @@ static int exynos_drm_crtc_mode_set_commit(struct drm_crtc 
*crtc, int x, int y,
                return -EPERM;
        }

+       /* when framebuffer is removed, commit should not proceed. */
+       if(!plane->fb){
+               DRM_ERROR("framebuffer has been removed from plane.\n");
+               return -EFAULT;
+       }
+
        crtc_w = crtc->primary->fb->width - x;
        crtc_h = crtc->primary->fb->height - y;

-- 
1.7.9.5