drm: Avoid connector reference imbalance on error path

Whilst looking at the fallout from using connector references for
atomic, I noticed that there is an early return buried in
drm_atomic_set_crtc_for_connector() that if hit could cause us to leak a
reference on the connector.

Fixes: d2307dea14 (drm/atomic: use connector references (v3))
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Stone <daniels@collabora.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1462535265-13058-1-git-send-email-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 86e89db02ed72b915580b1046c6d29ca032c9e29..3ff1ed7b33dbeb74aa036204f90931958eb5ee23 100644 (file)
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1160,14 +1160,18 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 {
        struct drm_crtc_state *crtc_state;
 
-       if (crtc)
-               drm_connector_reference(conn_state->connector);
-       if (conn_state->crtc && conn_state->crtc != crtc) {
+       if (conn_state->crtc == crtc)
+               return 0;
+
+       if (conn_state->crtc) {
                crtc_state = drm_atomic_get_existing_crtc_state(conn_state->state,
                                                                conn_state->crtc);
 
                crtc_state->connector_mask &=
                        ~(1 << drm_connector_index(conn_state->connector));
+
+               drm_connector_unreference(conn_state->connector);
+               conn_state->crtc = NULL;
        }
 
        if (crtc) {
@@ -1177,18 +1181,16 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 
                crtc_state->connector_mask |=
                        1 << drm_connector_index(conn_state->connector);
-       }
 
-       if (conn_state->crtc)
-               drm_connector_unreference(conn_state->connector);
-       conn_state->crtc = crtc;
+               drm_connector_reference(conn_state->connector);
+               conn_state->crtc = crtc;
 
-       if (crtc)
                DRM_DEBUG_ATOMIC("Link connector state %p to [CRTC:%d:%s]\n",
                                 conn_state, crtc->base.id, crtc->name);
-       else
+       } else {
                DRM_DEBUG_ATOMIC("Link connector state %p to [NOCRTC]\n",
                                 conn_state);
+       }
 
        return 0;
 }