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Merge bitcoin/bitcoin#21909: fuzz: Limit max insertions in timedata fuzz test

fa95555a49 fuzz: Limit max insertions in timedata fuzz test (MarcoFalke)

Pull request description:

  It is debatable whether a size of the median filter other than `200` (the only size used in production) should be fuzzed. For now add a minimal patch to cap the max insertions. Otherwise the complexity is N^2 log(N), where N is the size of the fuzz input.

  Hopefully fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=34167

ACKs for top commit:
  practicalswift:
    cr ACK fa95555a49: patch looks correct

Tree-SHA512: be7737e9f4c906053e355641de84dde31fed37ed6be4c5e92e602ca7675dffdaf06b7063b9235ef541b05d3d5fd689c99479317473bb15cb5271b8baabffd0f2
This commit is contained in:
MarcoFalke 2021-05-11 20:32:17 +02:00
commit 88dc09d759
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@ -15,10 +15,12 @@ FUZZ_TARGET(timedata)
{
FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
const unsigned int max_size = fuzzed_data_provider.ConsumeIntegralInRange<unsigned int>(0, 1000);
// A max_size of 0 implies no limit, so cap the max number of insertions to avoid timeouts
auto max_to_insert = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 4000);
// Divide by 2 to avoid signed integer overflow in .median()
const int64_t initial_value = fuzzed_data_provider.ConsumeIntegral<int64_t>() / 2;
CMedianFilter<int64_t> median_filter{max_size, initial_value};
while (fuzzed_data_provider.remaining_bytes() > 0) {
while (fuzzed_data_provider.remaining_bytes() > 0 && --max_to_insert >= 0) {
(void)median_filter.median();
assert(median_filter.size() > 0);
assert(static_cast<size_t>(median_filter.size()) == median_filter.sorted().size());