[PATCH] drm: check for garbage in unused addfb2 fields

[Daniel Vetter]

Unfortunately old userspace didn't clear this properly, but since
we've added fb modifiers that's fixed. Checking properly that unused
fields is important for abi extensions, and just right now there's a
bunch of discussions going on about how exactly the additional aux
planes for render compression should be specified.

So let's first make sure that the values in those additional fields
can be indeed used.

Cc: Thierry Reding <thierry.reding at gmail.com>
Testcase: igt/kms_addfb/unused-*
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/drm_crtc.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 2e26988a9762..8ad582f4026b 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -3308,6 +3308,32 @@ static int framebuffer_check(const struct drm_mode_fb_cmd2 *r)
 		}
 	}
 
+	for (i = num_planes; i < 4; i++) {
+		if (r->modifier[i]) {
+			DRM_DEBUG_KMS("non-zero modifier for unused plane %d\n", i);
+			return -EINVAL;
+		}
+
+		/* Pre-FB_MODIFIERS userspace didn't clear the structs properly. */
+		if (!(r->flags & DRM_MODE_FB_MODIFIERS))
+			continue;
+
+		if (r->handles[i]) {
+			DRM_DEBUG_KMS("buffer object handle for unused plane %d\n", i);
+			return -EINVAL;
+		}
+
+		if (r->pitches[i]) {
+			DRM_DEBUG_KMS("non-zero pitch for unused plane %d\n", i);
+			return -EINVAL;
+		}
+
+		if (r->offsets[i]) {
+			DRM_DEBUG_KMS("non-zero offset for unused plane %d\n", i);
+			return -EINVAL;
+		}
+	}
+
 	return 0;
 }
 
-- 
2.1.4