Security: Out-of-bounds tensor access from unvalidated edge indices

[tuanaiseo]

Problem

The CPU gather/scatter kernel reads vertex indices from edges and directly indexes output_a[v0], output_a[v1], input_a[v1], and input_a[v0] without validating bounds. A crafted edges tensor containing negative or too-large indices can trigger out-of-bounds reads/writes, leading to crashes or memory corruption in the extension process.

Severity: high
File: pytorch3d/csrc/gather_scatter/gather_scatter_cpu.cpp

Solution

Before the loop, validate edges index range with TORCH_CHECK (e.g., min >= 0 and max < num_vertices). Keep the same validation in CUDA and CPU paths, and fail fast on invalid input.

Changes

• pytorch3d/csrc/gather_scatter/gather_scatter_cpu.cpp (modified)

Testing

• Existing tests pass
• Manual review completed
• No new warnings/errors introduced

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