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>
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 67c1dc8..3624632 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -56,6 +56,8 @@
if (!state)
return NULL;
+ state->num_connector = ACCESS_ONCE(dev->mode_config.num_connector);
+
state->crtcs = kcalloc(dev->mode_config.num_crtc,
sizeof(*state->crtcs), GFP_KERNEL);
if (!state->crtcs)
@@ -72,12 +74,12 @@
sizeof(*state->plane_states), GFP_KERNEL);
if (!state->plane_states)
goto fail;
- state->connectors = kcalloc(dev->mode_config.num_connector,
+ state->connectors = kcalloc(state->num_connector,
sizeof(*state->connectors),
GFP_KERNEL);
if (!state->connectors)
goto fail;
- state->connector_states = kcalloc(dev->mode_config.num_connector,
+ state->connector_states = kcalloc(state->num_connector,
sizeof(*state->connector_states),
GFP_KERNEL);
if (!state->connector_states)
@@ -117,7 +119,7 @@
DRM_DEBUG_KMS("Clearing atomic state %p\n", state);
- for (i = 0; i < config->num_connector; i++) {
+ for (i = 0; i < state->num_connector; i++) {
struct drm_connector *connector = state->connectors[i];
if (!connector)
@@ -304,6 +306,21 @@
index = drm_connector_index(connector);
+ /*
+ * Construction of atomic state updates can race with a connector
+ * hot-add which might overflow. In this case flip the table and just
+ * restart the entire ioctl - no one is fast enough to livelock a cpu
+ * with physical hotplug events anyway.
+ *
+ * Note that we only grab the indexes once we have the right lock to
+ * prevent hotplug/unplugging of connectors. So removal is no problem,
+ * at most the array is a bit too large.
+ */
+ if (index >= state->num_connector) {
+ DRM_DEBUG_KMS("Hot-added connector would overflow state array, restarting\n");
+ return -EAGAIN;
+ }
+
if (state->connector_states[index])
return state->connector_states[index];
@@ -499,10 +516,9 @@
drm_atomic_connectors_for_crtc(struct drm_atomic_state *state,
struct drm_crtc *crtc)
{
- int nconnectors = state->dev->mode_config.num_connector;
int i, num_connected_connectors = 0;
- for (i = 0; i < nconnectors; i++) {
+ for (i = 0; i < state->num_connector; i++) {
struct drm_connector_state *conn_state;
conn_state = state->connector_states[i];