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 (file)
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -56,6 +56,8 @@ drm_atomic_state_alloc(struct drm_device *dev)
        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 @@ drm_atomic_state_alloc(struct drm_device *dev)
                                      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 @@ void drm_atomic_state_clear(struct drm_atomic_state *state)
 
        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 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state,
 
        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 @@ int
 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];

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 0cd0546..99095ef 100644 (file)
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -249,7 +249,6 @@ static int
 mode_fixup(struct drm_atomic_state *state)
 {
        int ncrtcs = state->dev->mode_config.num_crtc;
-       int nconnectors = state->dev->mode_config.num_connector;
        struct drm_crtc_state *crtc_state;
        struct drm_connector_state *conn_state;
        int i;
@@ -264,7 +263,7 @@ mode_fixup(struct drm_atomic_state *state)
                drm_mode_copy(&crtc_state->adjusted_mode, &crtc_state->mode);
        }
 
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < state->num_connector; i++) {
                struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
 
@@ -336,7 +335,6 @@ drm_atomic_helper_check_prepare(struct drm_device *dev,
                                struct drm_atomic_state *state)
 {
        int ncrtcs = dev->mode_config.num_crtc;
-       int nconnectors = dev->mode_config.num_connector;
        struct drm_crtc *crtc;
        struct drm_crtc_state *crtc_state;
        int i, ret;
@@ -361,7 +359,7 @@ drm_atomic_helper_check_prepare(struct drm_device *dev,
                }
        }
 
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < state->num_connector; i++) {
                /*
                 * This only sets crtc->mode_changed for routing changes,
                 * drivers must set crtc->mode_changed themselves when connector
@@ -485,10 +483,9 @@ static void
 disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 {
        int ncrtcs = old_state->dev->mode_config.num_crtc;
-       int nconnectors = old_state->dev->mode_config.num_connector;
        int i;
 
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < old_state->num_connector; i++) {
                struct drm_connector_state *old_conn_state;
                struct drm_connector *connector;
                struct drm_encoder_helper_funcs *funcs;
@@ -553,12 +550,11 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 static void
 set_routing_links(struct drm_device *dev, struct drm_atomic_state *old_state)
 {
-       int nconnectors = dev->mode_config.num_connector;
        int ncrtcs = old_state->dev->mode_config.num_crtc;
        int i;
 
        /* clear out existing links */
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < old_state->num_connector; i++) {
                struct drm_connector *connector;
 
                connector = old_state->connectors[i];
@@ -573,7 +569,7 @@ set_routing_links(struct drm_device *dev, struct drm_atomic_state *old_state)
        }
 
        /* set new links */
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < old_state->num_connector; i++) {
                struct drm_connector *connector;
 
                connector = old_state->connectors[i];
@@ -608,7 +604,6 @@ static void
 crtc_set_mode(struct drm_device *dev, struct drm_atomic_state *old_state)
 {
        int ncrtcs = old_state->dev->mode_config.num_crtc;
-       int nconnectors = old_state->dev->mode_config.num_connector;
        int i;
 
        for (i = 0; i < ncrtcs; i++) {
@@ -626,7 +621,7 @@ crtc_set_mode(struct drm_device *dev, struct drm_atomic_state *old_state)
                        funcs->mode_set_nofb(crtc);
        }
 
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < old_state->num_connector; i++) {
                struct drm_connector *connector;
                struct drm_crtc_state *new_crtc_state;
                struct drm_encoder_helper_funcs *funcs;
@@ -687,7 +682,6 @@ void drm_atomic_helper_commit_post_planes(struct drm_device *dev,
                                          struct drm_atomic_state *old_state)
 {
        int ncrtcs = old_state->dev->mode_config.num_crtc;
-       int nconnectors = old_state->dev->mode_config.num_connector;
        int i;
 
        for (i = 0; i < ncrtcs; i++) {
@@ -706,7 +700,7 @@ void drm_atomic_helper_commit_post_planes(struct drm_device *dev,
                        funcs->commit(crtc);
        }
 
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < old_state->num_connector; i++) {
                struct drm_connector *connector;
                struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
@@ -1304,7 +1298,6 @@ static int update_output_state(struct drm_atomic_state *state,
 {
        struct drm_device *dev = set->crtc->dev;
        struct drm_connector_state *conn_state;
-       int nconnectors = state->dev->mode_config.num_connector;
        int ncrtcs = state->dev->mode_config.num_crtc;
        int ret, i, j;
 
@@ -1333,7 +1326,7 @@ static int update_output_state(struct drm_atomic_state *state,
        }
 
        /* Then recompute connector->crtc links and crtc enabling state. */
-       for (i = 0; i < nconnectors; i++) {
+       for (i = 0; i < state->num_connector; i++) {
                struct drm_connector *connector;
 
                connector = state->connectors[i];

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 7b28ab0..f3142c6 100644 (file)
--- 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;