drm: Don't leak phys_wc "handles" to userspace

I didn't fix this in the earlier patch -- it would have broken the
build due to the now-deleted garbage in drm_os_linux.h.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c
index 0190fce20078..5a4dbb410b71 100644
--- a/drivers/gpu/drm/drm_bufs.c
+++ b/drivers/gpu/drm/drm_bufs.c
@@ -414,6 +414,15 @@ int drm_addmap_ioctl(struct drm_device *dev, void *data,
 
         /* avoid a warning on 64-bit, this casting isn't very nice, but the API is set so too late */
         map->handle = (void *)(unsigned long)maplist->user_token;
+
+        /*
+         * It appears that there are no users of this value whatsoever --
+         * drmAddMap just discards it.  Let's not encourage its use.
+         * (Keeping drm_addmap_core's returned mtrr value would be wrong --
+         *  it's not a real mtrr index anymore.)
+         */
+        map->mtrr = -1;
+
         return 0;
 }