fuzz: reset chainman after external block imports #36129

pull HowHsu wants to merge 1 commits into bitcoin:master from HowHsu:fuzz-reset-load-external-chainman changing 1 files +12 −2

HowHsu commented at 1:45 PM on August 31, 2026: contributor

LoadExternalBlockFile() may add headers to the block index even when full block validation fails. Reusing the static chainman therefore lets one fuzz input affect later inputs and makes all-corpus coverage order-dependent.

Recreate the chainman after each processed input, disable unused network setup so PeerManager cannot retain a reference to it, and reseed the deterministic test RNG consumed by chainman initialization.

Tested with run_deterministic_fuzz_coverage.sh load_external_block_file 20: all 930 corpus inputs passed both the individual-repeat and randomized all-corpus checks.

fuzz: reset chainman after external block imports

LoadExternalBlockFile may add headers to the block index even when
full block validation fails. Reusing the static chainman lets one fuzz
input affect later inputs and makes shuffled corpus coverage
order-dependent.

Recreate the chainman after each processed input to restore the genesis
baseline. Disable unused network setup so PeerManager cannot retain a
reference to the replaced chainman. Reseed the test RNG because
chainman initialization consumes the global deterministic random state.

0243779e73

DrahtBot added the label Fuzzing on Aug 31, 2026
DrahtBot commented at 1:45 PM on August 31, 2026: contributor



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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36129.



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fuzz: reset chainman after external block imports #36129

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