[rsyncable] Ensure ZSTD_compressBound() is respected #2776
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Cyan4973
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Sep 14, 2021
lib/compress/zstdmt_compress.c
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| * This stops us from regressing compression ratio too much, | ||
| * and ensures our output fits in ZSTD_compressBound(). | ||
| * | ||
| * If this is shrunk < ZSTD_BLOCKSIXELOG_MIN then |
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nit: ZSTD_BLOCKSIXELOG_MIN
In degenerate cases `--rsyncable` could create very small blocks (1 byte). This causes the compressed output to be larger than `ZSTD_compressBound()`. Fix the issue by ensuring that rsyncable mode never outputs blocks smaller than 128 KB. The minimum job size is 512 KB, so we shouldn't lose many synchronization points from skipping any that cause blocks smaller than 128 KB. And even if we do, that is fine, because we'll find the next one. This fixes the `raw_dictionary_round_trip` oss-fuzz assert. Credit to OSS-Fuzz
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In degenerate cases
--rsyncablecould create very small blocks (1byte). This causes the compressed output to be larger than
ZSTD_compressBound(). Fix the issue by ensuring that rsyncable modenever outputs blocks smaller than 128 KB.
The minimum job size is 512 KB, so we shouldn't lose many
synchronization points from skipping any that cause blocks smaller than
128 KB. And even if we do, that is fine, because we'll find the next
one.
This fixes the
raw_dictionary_round_triposs-fuzz assert.Credit to OSS-Fuzz