From 91c9f341377ea496ca08a2eab32ba7d5b2ce0893 Mon Sep 17 00:00:00 2001
From: Yann Noutary <ynoutary@meta.com>
Date: Wed, 20 Nov 2024 01:24:28 -0800
Subject: [PATCH] Add safeguard in case num_tris diverges

Summary:
This PR fixes adds a safeguard preventing num_tris to overflow in `MAX_TRIS`-length arrays. The update rule of `num_tris` is bounded :

 - max(num_tris(t)) = 2*num_tris(t-1)
 - num_tris(0) = 12
 - t <= 6

So :
 - max(num_tris) = 2^6*12
 - max(num_tris) = 768

Reviewed By: bottler

Differential Revision: D66162573

fbshipit-source-id: e269a79c75c6cc33306986b1f1256cffbe96c730
---
 pytorch3d/csrc/iou_box3d/iou_utils.cuh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pytorch3d/csrc/iou_box3d/iou_utils.cuh b/pytorch3d/csrc/iou_box3d/iou_utils.cuh
index 5ad5b165..c4a1f5c9 100644
--- a/pytorch3d/csrc/iou_box3d/iou_utils.cuh
+++ b/pytorch3d/csrc/iou_box3d/iou_utils.cuh
@@ -728,7 +728,7 @@ __device__ inline int BoxIntersections(
       }
     }
     // Update the face_verts_out tris
-    num_tris = offset;
+    num_tris = min(MAX_TRIS, offset);
     for (int j = 0; j < num_tris; ++j) {
       face_verts_out[j] = tri_verts_updated[j];
     }