James Simmons wrote:

quoted

@@ -905,6 +905,9 @@ int drm_fb_helper_single_fb_probe(struct
 
 	if (new_fb) {
 		info->var.pixclock = 0;
+		ret = fb_alloc_cmap(&info->cmap, crtc->gamma_size, 0);
+		if (ret)
+			return ret;

quoted

 		if (register_framebuffer(info) < 0) {

			fb_dealloc_cmap(info->cmap);	

quoted

 			return -EINVAL;

		}

Plug memory leak.

Oops.  Thanks again.
New patch set follows:

 include/drm/drm_crtc.h          |    2 +-
 drivers/gpu/drm/drm_fb_helper.c |   14 ++++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

v2: incorporated suggestions by James Simmons
v3: bugfix by James Simmons