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Fix traversal buffer size overflow - #31
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tbybell merged 2 commits intoOct 18, 2026
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Problem: A value change section can declare a traversal size near 2**64. Adding the 67 bytes of decompression and varint slack wraps the allocation size to a value smaller than 67, leading the chain decompressor to do a out-of-bounds buffer access Solution: reject sizes that would overflow before adding the overhead. That check jumps to `block_err` before `chain_cmem` is allocated, so also initialize `chain_cmem` to NULL and reset it after freeing it, to avoid freeing it while uninitialized or freeing it twice. AI-assisted
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Problem: A value change section can declare a traversal size near 2**64. Adding the 67 bytes of decompression and varint slack wraps the allocation size to a value smaller than 67, leading the chain decompressor to do a out-of-bounds buffer access
Solution: reject sizes that would overflow before adding the overhead. That check jumps to
block_errbeforechain_cmemis allocated, so also initializechain_cmemto NULL and reset it after freeing it, to avoid freeing it while uninitialized or freeing it twice.AI-assisted