Fix integer overflow in ReadBlock block size calculation#1308
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nsknv wants to merge 2 commits intogoogle:mainfrom
Open
Fix integer overflow in ReadBlock block size calculation#1308nsknv wants to merge 2 commits intogoogle:mainfrom
nsknv wants to merge 2 commits intogoogle:mainfrom
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In ReadBlock(), the expression `n + kBlockTrailerSize` can overflow when `handle.size()` is close to SIZE_MAX, wrapping to a small value. This causes an undersized heap allocation followed by an out-of-bounds read when the code accesses `data[n]`, crashing the process. Add an overflow check before the allocation to detect and reject block handles with sizes that would cause the addition to wrap.
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Referencing google issue tracker ID: 493717816 |
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@pwnall - please review. |
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Summary
ReadBlock()wheren + kBlockTrailerSizewraps whenhandle.size()is nearSIZE_MAX, bypassing the truncation check and causing an out-of-bounds heap read atdata[n]Details
BlockHandle::size_is decoded from varint64 with no upper-bound validation. When the size is close toSIZE_MAX, the additionn + kBlockTrailerSize(wherekBlockTrailerSizeis 5) wraps to a small value. This causes:new char[wrapped_value])data[n]reads out of bounds, crashing the processThe fix adds an overflow check before the allocation.