drm/atomic: Don't overrun the connector array when hotplugging

Yet another fallout from not considering DP MST hotplug. With the
previous patches we have stable indices, but it might still happen
that a connector gets added between when we allocate the array and
when we actually add a connector. Especially when we back off due to
ww mutex contention or similar issues.

So store the sizes of the arrays in struct drm_atomic_state and double
check them. We don't really care about races except that we want to
use a consistent value, so ACCESS_ONCE is all we need. And if we
indeed notice that we'd overrun the array then just give up and
restart the entire ioctl.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 7b28ab032a88..f3142c64e3d5 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -825,6 +825,7 @@ struct drm_bridge {
  * @plane_states: pointer to array of plane states pointers
  * @crtcs: pointer to array of CRTC pointers
  * @crtc_states: pointer to array of CRTC states pointers
+ * @num_connector: size of the @connectors and @connector_states arrays
  * @connectors: pointer to array of connector pointers
  * @connector_states: pointer to array of connector states pointers
  * @acquire_ctx: acquire context for this atomic modeset state update
@@ -836,6 +837,7 @@ struct drm_atomic_state {
         struct drm_plane_state **plane_states;
         struct drm_crtc **crtcs;
         struct drm_crtc_state **crtc_states;
+        int num_connector;
         struct drm_connector **connectors;
         struct drm_connector_state **connector_states;