[PATCH 2/2] drm/atomic: Fix freeing connector/plane state too early by tracking commits

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Currently we neatly track the crtc state, but forget to look at
plane/connector state.

When doing a nonblocking modeset, immediately followed by a setprop
before the modeset completes, the setprop will see the modesets new
state as the old state and free it.

This has to be solved by waiting for hw_done on the connector, even
if it's not assigned to a crtc. When a connector is unbound we take
the last crtc commit, and when it stays unbound we create a new
crtc commit for the connector that gets signaled on hw_done.

We wait for it the same way as we do for crtc's, which will make
sure we never run into a use-after-free situation.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Testcase: kms_atomic_transition.plane-use-after-nonblocking-unbind*
Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_atomic_helper.c | 171 ++++++++++++++++++++++++++++++++++--
 include/drm/drm_connector.h         |   7 ++
 include/drm/drm_plane.h             |   7 ++
 3 files changed, 179 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 9c2888cb4081..a4fd500d6200 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1644,6 +1644,39 @@ static void release_crtc_commit(struct completion *completion)
 	drm_crtc_commit_put(commit);
 }
 
+static void init_commit(struct drm_crtc_commit *commit, struct drm_crtc *crtc)
+{
+	init_completion(&commit->flip_done);
+	init_completion(&commit->hw_done);
+	init_completion(&commit->cleanup_done);
+	INIT_LIST_HEAD(&commit->commit_entry);
+	kref_init(&commit->ref);
+	commit->crtc = crtc;
+}
+
+static struct drm_crtc_commit *
+init_or_ref_crtc_commit(struct drm_atomic_state *state, struct drm_crtc *crtc)
+{
+	struct drm_crtc_commit *commit;
+
+	if (crtc) {
+		struct drm_crtc_state *new_crtc_state;
+
+		new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+
+		commit = new_crtc_state->commit;
+		drm_crtc_commit_get(commit);
+	} else {
+		commit = kzalloc(sizeof(*commit), GFP_KERNEL);
+		if (!commit)
+			return NULL;
+
+		init_commit(commit, NULL);
+	}
+
+	return commit;
+}
+
 /**
  * drm_atomic_helper_setup_commit - setup possibly nonblocking commit
  * @state: new modeset state to be committed
@@ -1692,6 +1725,10 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
+	struct drm_connector *conn;
+	struct drm_connector_state *old_conn_state, *new_conn_state;
+	struct drm_plane *plane;
+	struct drm_plane_state *old_plane_state, *new_plane_state;
 	struct drm_crtc_commit *commit;
 	int i, ret;
 
@@ -1700,12 +1737,7 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 		if (!commit)
 			return -ENOMEM;
 
-		init_completion(&commit->flip_done);
-		init_completion(&commit->hw_done);
-		init_completion(&commit->cleanup_done);
-		INIT_LIST_HEAD(&commit->commit_entry);
-		kref_init(&commit->ref);
-		commit->crtc = crtc;
+		init_commit(commit, crtc);
 
 		new_crtc_state->commit = commit;
 
@@ -1741,6 +1773,36 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 		drm_crtc_commit_get(commit);
 	}
 
+	for_each_oldnew_connector_in_state(state, conn, old_conn_state, new_conn_state, i) {
+		if (new_conn_state->crtc)
+			continue;
+
+		if (nonblock && old_conn_state->commit &&
+		    !try_wait_for_completion(&old_conn_state->commit->flip_done))
+			return -EBUSY;
+
+		commit = init_or_ref_crtc_commit(state, old_conn_state->crtc);
+		if (!commit)
+			return -ENOMEM;
+
+		new_conn_state->commit = commit;
+	}
+
+	for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
+		if (new_plane_state->crtc)
+			continue;
+
+		if (nonblock && old_plane_state->commit &&
+		    !try_wait_for_completion(&old_plane_state->commit->flip_done))
+			return -EBUSY;
+
+		commit = init_or_ref_crtc_commit(state, old_plane_state->crtc);
+		if (!commit)
+			return -ENOMEM;
+
+		new_plane_state->commit = commit;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_atomic_helper_setup_commit);
@@ -1761,6 +1823,10 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *old_crtc_state;
+	struct drm_plane *plane;
+	struct drm_plane_state *old_plane_state;
+	struct drm_connector *conn;
+	struct drm_connector_state *old_conn_state;
 	struct drm_crtc_commit *commit;
 	int i;
 	long ret;
@@ -1785,6 +1851,48 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
 			DRM_ERROR("[CRTC:%d:%s] flip_done timed out\n",
 				  crtc->base.id, crtc->name);
 	}
+
+	for_each_old_connector_in_state(old_state, conn, old_conn_state, i) {
+		commit = old_conn_state->commit;
+
+		if (!commit)
+			continue;
+
+		ret = wait_for_completion_timeout(&commit->hw_done,
+						  10*HZ);
+		if (ret == 0)
+			DRM_ERROR("[CONNECTOR:%d:%s] hw_done timed out\n",
+				  conn->base.id, conn->name);
+
+		/* Currently no support for overwriting flips, hence
+		 * stall for previous one to execute completely. */
+		ret = wait_for_completion_timeout(&commit->flip_done,
+						  10*HZ);
+		if (ret == 0)
+			DRM_ERROR("[CONNECTOR:%d:%s] flip_done timed out\n",
+				  conn->base.id, conn->name);
+	}
+
+	for_each_old_plane_in_state(old_state, plane, old_plane_state, i) {
+		commit = old_plane_state->commit;
+
+		if (!commit)
+			continue;
+
+		ret = wait_for_completion_timeout(&commit->hw_done,
+						  10*HZ);
+		if (ret == 0)
+			DRM_ERROR("[PLANE:%d:%s] hw_done timed out\n",
+				  plane->base.id, plane->name);
+
+		/* Currently no support for overwriting flips, hence
+		 * stall for previous one to execute completely. */
+		ret = wait_for_completion_timeout(&commit->flip_done,
+						  10*HZ);
+		if (ret == 0)
+			DRM_ERROR("[PLANE:%d:%s] flip_done timed out\n",
+				  plane->base.id, plane->name);
+	}
 }
 EXPORT_SYMBOL(drm_atomic_helper_wait_for_dependencies);
 
@@ -1807,6 +1915,10 @@ void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *new_crtc_state;
+	struct drm_connector *conn;
+	struct drm_connector_state *new_conn_state;
+	struct drm_plane *plane;
+	struct drm_plane_state *new_plane_state;
 	struct drm_crtc_commit *commit;
 	int i;
 
@@ -1819,6 +1931,23 @@ void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
 		WARN_ON(new_crtc_state->event);
 		complete_all(&commit->hw_done);
 	}
+
+	for_each_new_connector_in_state(old_state, conn, new_conn_state, i) {
+		commit = new_conn_state->commit;
+		if (commit && !commit->crtc) {
+			complete_all(&commit->hw_done);
+			complete_all(&commit->flip_done);
+		}
+	}
+
+	for_each_new_plane_in_state(old_state, plane, new_plane_state, i) {
+		commit = new_plane_state->commit;
+		if (commit && !commit->crtc) {
+			complete_all(&commit->hw_done);
+			complete_all(&commit->flip_done);
+		}
+	}
+
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);
 
@@ -2258,6 +2387,28 @@ int drm_atomic_helper_swap_state(struct drm_atomic_state *state,
 			if (ret)
 				return ret;
 		}
+
+		for_each_old_connector_in_state(state, connector, old_conn_state, i) {
+			commit = old_conn_state->commit;
+
+			if (!commit)
+				continue;
+
+			ret = wait_for_completion_interruptible(&commit->hw_done);
+			if (ret)
+				return ret;
+		}
+
+		for_each_old_plane_in_state(state, plane, old_plane_state, i) {
+			commit = old_plane_state->commit;
+
+			if (!commit)
+				continue;
+
+			ret = wait_for_completion_interruptible(&commit->hw_done);
+			if (ret)
+				return ret;
+		}
 	}
 
 	for_each_oldnew_connector_in_state(state, connector, old_conn_state, new_conn_state, i) {
@@ -3240,6 +3391,7 @@ void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
 		drm_framebuffer_get(state->fb);
 
 	state->fence = NULL;
+	state->commit = NULL;
 }
 EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
 
@@ -3281,6 +3433,9 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
 
 	if (state->fence)
 		dma_fence_put(state->fence);
+
+	if (state->commit)
+		drm_crtc_commit_put(state->commit);
 }
 EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
 
@@ -3359,6 +3514,7 @@ __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
 	memcpy(state, connector->state, sizeof(*state));
 	if (state->crtc)
 		drm_connector_get(connector);
+	state->commit = NULL;
 }
 EXPORT_SYMBOL(__drm_atomic_helper_connector_duplicate_state);
 
@@ -3485,6 +3641,9 @@ __drm_atomic_helper_connector_destroy_state(struct drm_connector_state *state)
 {
 	if (state->crtc)
 		drm_connector_put(state->connector);
+
+	if (state->commit)
+		drm_crtc_commit_put(state->commit);
 }
 EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ea8da401c93c..8837649d16e8 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -347,6 +347,13 @@ struct drm_connector_state {
 
 	struct drm_atomic_state *state;
 
+	/**
+	 * @commit: Tracks the pending commit to prevent use-after-free conditions.
+	 *
+	 * Is only set when @crtc is NULL.
+	 */
+	struct drm_crtc_commit *commit;
+
 	struct drm_tv_connector_state tv;
 
 	/**
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 73f90f9d057f..7d96116fd4c4 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -123,6 +123,13 @@ struct drm_plane_state {
 	 */
 	bool visible;
 
+	/**
+	 * @commit: Tracks the pending commit to prevent use-after-free conditions.
+	 *
+	 * Is only set when @crtc is NULL.
+	 */
+	struct drm_crtc_commit *commit;
+
 	struct drm_atomic_state *state;
 };
 
-- 
2.11.0

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