drm: Reject getfb for multi-plane framebuffers

getfb can only return a single plane, so reject attempts to use it with
multi-plane framebuffers.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reported-by: Daniel van Vugt <daniel.van.vugt@canonical.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Fixes: 308e5bc ("drm: add an fb creation ioctl that takes a pixel format v5")
Cc: stable@vger.kernel.org # v3.3+
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105518
Link: https://patchwork.freedesktop.org/patch/msgid/20180320225839.30905-1-daniels@collabora.com

drivers/gpu/drm/drm_framebuffer.c

@@ -461,6 +461,12 @@ int drm_mode_getfb(struct drm_device *dev,
 	if (!fb)
 		return -ENOENT;
 
+	/* Multi-planar framebuffers need getfb2. */
+	if (fb->format->num_planes > 1) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	r->height = fb->height;
 	r->width = fb->width;
 	r->depth = fb->format->depth;
@@ -484,6 +490,7 @@ int drm_mode_getfb(struct drm_device *dev,
 		ret = -ENODEV;
 	}
 
+out:
 	drm_framebuffer_put(fb);
 
 	return ret;