The DRM core setplane code should check that the plane is usable on the
specified CRTC before calling into the driver.

Prior to this patch, a plane's possible_crtcs field was purely
informational for userspace and was never actually verified at the
kernel level (aside from the primary plane helper).

Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/drm_crtc.c         | 7 +++++++
 drivers/gpu/drm/drm_plane_helper.c | 6 ------
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 461d19b..b6d6c04 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2140,6 +2140,13 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
        }
        crtc = obj_to_crtc(obj);

+       /* Check whether this plane is usable on this CRTC */
+       if (!(plane->possible_crtcs & drm_crtc_mask(crtc))) {
+               DRM_DEBUG_KMS("Invalid crtc for plane\n");
+               ret = -EINVAL;
+               goto out;
+       }
+
        fb = drm_framebuffer_lookup(dev, plane_req->fb_id);
        if (!fb) {
                DRM_DEBUG_KMS("Unknown framebuffer ID %d\n",
diff --git a/drivers/gpu/drm/drm_plane_helper.c 
b/drivers/gpu/drm/drm_plane_helper.c
index d966afa..b601233 100644
--- a/drivers/gpu/drm/drm_plane_helper.c
+++ b/drivers/gpu/drm/drm_plane_helper.c
@@ -137,12 +137,6 @@ int drm_primary_helper_update(struct drm_plane *plane, 
struct drm_crtc *crtc,
                return -EINVAL;
        }

-       /* Primary planes are locked to their owning CRTC */
-       if (plane->possible_crtcs != drm_crtc_mask(crtc)) {
-               DRM_DEBUG_KMS("Cannot change primary plane CRTC\n");
-               return -EINVAL;
-       }
-
        /* Disallow scaling */
        src_w >>= 16;
        src_h >>= 16;
-- 
1.8.5.1

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