[Intel-gfx] [PATCH 2/3] drm/atomic: Refuse to steal encoders with index < conn_idx.

[Maarten Lankhorst]

There was a potential to crash in the following case:
[   49.985270] [drm:update_connector_routing] Updating routing for [CONNECTOR:48:DP-3]
[   49.985273] [drm:update_connector_routing] [CONNECTOR:48:DP-3] keeps [ENCODER:33:DP MST-33], now on [CRTC:21:crtc-0]
[   49.985275] [drm:update_connector_routing] Updating routing for [CONNECTOR:51:DP-4]
[   49.985278] [drm:steal_encoder] [ENCODER:33:DP MST-33] in use on [CRTC:21:crtc-0], stealing it
[   49.985281] [drm:update_connector_routing] [CONNECTOR:51:DP-4] using [ENCODER:33:DP MST-33] on [CRTC:21:crtc-0]

This case is not allowed, similar to the previous case of 2 connectors newly assigned to the same encoder.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index fc1c06b1d8bb..fa708559542c 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -88,18 +88,18 @@ drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
 
 static bool
 check_pending_encoder_assignment(struct drm_atomic_state *state,
-				 struct drm_encoder *new_encoder)
+				 struct drm_encoder *new_encoder,
+				 int conn_idx)
 {
 	struct drm_connector *connector;
 	struct drm_connector_state *conn_state;
 	int i;
 
 	for_each_connector_in_state(state, connector, conn_state, i) {
-		if (conn_state->best_encoder != new_encoder)
-			continue;
+		if (i >= conn_idx)
+			break;
 
-		/* encoder already assigned and we're trying to re-steal it! */
-		if (connector->state->best_encoder != conn_state->best_encoder)
+		if (conn_state->best_encoder == new_encoder)
 			return false;
 	}
 
@@ -272,7 +272,7 @@ update_connector_routing(struct drm_atomic_state *state,
 		return 0;
 	}
 
-	if (!check_pending_encoder_assignment(state, new_encoder)) {
+	if (!check_pending_encoder_assignment(state, new_encoder, conn_idx)) {
 		DRM_DEBUG_ATOMIC("Encoder for [CONNECTOR:%d:%s] already assigned\n",
 				 connector->base.id,
 				 connector->name);
-- 
2.1.0