fix(kdtree): guard against zero-dimensional attributes and heap-allocate decoder (fixes #1103) - #1224
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…ate decoder (fixes google#1103) In KdTreeAttributesDecoder::DecodePortableAttributes() and DecodeDataNeededByPortableTransforms(), when malformed input specifies 0 attributes or 0 components across attributes, total_dimensionality evaluates to 0. A 0-dimensional KdTree causes division by zero in DRACO_INCREMENT_MOD(last_axis, dimension_), out-of-bounds index on empty level/base vectors, and invalid memory dereferences (CWE-476 / CWE-125). Furthermore, allocating DynamicIntegerPointsKdTreeDecoder<level_t> on the stack inside DecodePoints creates heavy stack frame overhead with nested decoder arrays, which can cause stack-buffer-overflows in tight stack environments. This commit: 1. Validates total_dimensionality > 0 in DecodePortableAttributes() and DecodeDataNeededByPortableTransforms(). 2. Validates dimension_ > 0 in DynamicIntegerPointsKdTreeDecoder::DecodePoints(). 3. Dynamically allocates DynamicIntegerPointsKdTreeDecoder on the heap via std::unique_ptr in DecodePoints(). 4. Adds a unit test RejectZeroDimensionalAttributes in point_cloud_kd_tree_encoding_test.cc. Fixes google#1103.
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Summary of Changes
Fixes #1103 (Crash/SEGV in
draco::DecoderBuffer::Peek/DynamicIntegerPointsKdTreeDecoderdue to unvalidated 0-dimensional attribute decoding).Problem
total_dimensionalityinKdTreeAttributesDecoderevaluates to 0. A 0-dimensional KdTree is invalid (point clouds require at least 1 spatial dimension), and passingdimension_ == 0intoDynamicIntegerPointsKdTreeDecodercauses:DRACO_INCREMENT_MOD(last_axis, dimension_)levels_andbase_stack_vectorsPointAttributeVectorOutputIteratorDynamicIntegerPointsKdTreeDecoder<level_t>on the stack inDecodePoints()creates significant stack bloat across all compression levels (0 through 6), which can trigger stack buffer exhaustion.Fix
total_dimensionality > 0inKdTreeAttributesDecoder::DecodePortableAttributes()andDecodeDataNeededByPortableTransforms().dimension_ > 0inDynamicIntegerPointsKdTreeDecoder::DecodePoints().DynamicIntegerPointsKdTreeDecoderon the heap viastd::unique_ptrinDecodePoints()to minimize stack frame size.RejectZeroDimensionalAttributesinsrc/draco/compression/point_cloud/point_cloud_kd_tree_encoding_test.cc.