From ca0225c0fd38b4362c2e05a3f79eaacf883fcb49 Mon Sep 17 00:00:00 2001 From: fanquake Date: Fri, 15 Sep 2023 10:08:02 +0100 Subject: [PATCH] Merge bitcoin/bitcoin#28480: fuzz: Don't use afl++ deferred forkserver mode 508d05f8a7b511dd53f543df8899813487eb03e5 [fuzz] Don't use afl++ deferred forkserver mode (dergoegge) Pull request description: Fixes #28469 This makes our afl++ harness essentially behave like libFuzzer, with the exception that the whole program does fully reset every 100000 iterations. 100000 is somewhat arbitrary and we could also go with `std::numeric_limits::max()` but a smaller limit does allow for the occasional reset to counter act some amount of instability in the fuzzing loop (e.g. non-determinism, statefulness). It's a bit of a shame to do this just for the targets whose initial state can't be forked (e.g. threads) because other targets do benefit from not having to redo the state setup. An alternative would be https://github.com/bitcoin/bitcoin/issues/28469#issuecomment-1717526774: ``` If the goal is to be maximally performant, the fork would need to happen for each fuzz target specifically. I guess it can be achieved by wrapping __AFL_INIT(); into a helper function and then require all fuzz target initialize() to call it? ``` ACKs for top commit: MarcoFalke: lgtm ACK 508d05f8a7b511dd53f543df8899813487eb03e5 Tree-SHA512: d9fe94e2e3198795f8fb58f67eb383531a534bcd4ec75a1f0ae6ccb5531863dbc09800bb7d77536417745c4c8bc49a4f84dcc959918b27d4997a270eeacb0e7e --- src/test/fuzz/fuzz.cpp | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/src/test/fuzz/fuzz.cpp b/src/test/fuzz/fuzz.cpp index 8319a8f52d..5ed10f1a21 100644 --- a/src/test/fuzz/fuzz.cpp +++ b/src/test/fuzz/fuzz.cpp @@ -170,17 +170,11 @@ int main(int argc, char** argv) { initialize(); static const auto& test_one_input = *Assert(g_test_one_input); -#ifdef __AFL_HAVE_MANUAL_CONTROL - // Enable AFL deferred forkserver mode. Requires compilation using - // afl-clang-fast++. See fuzzing.md for details. - __AFL_INIT(); -#endif - #ifdef __AFL_LOOP // Enable AFL persistent mode. Requires compilation using afl-clang-fast++. // See fuzzing.md for details. const uint8_t* buffer = __AFL_FUZZ_TESTCASE_BUF; - while (__AFL_LOOP(1000)) { + while (__AFL_LOOP(100000)) { size_t buffer_len = __AFL_FUZZ_TESTCASE_LEN; test_one_input({buffer, buffer_len}); }