Nothing to do here, just leaving a note for reference.
When building the ci_native_fuzz_msan CI pod, and running inside of the pod a fuzz worker, it will report use-of-uninitialized-value inside libfuzzer.
0FUZZ=parse_univalue /ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/src/test/fuzz/fuzz -max_total_time=1 # works
0FUZZ=parse_univalue /ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/src/test/fuzz/fuzz -max_total_time=1 -jobs=1 # fails
1
2
3/ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/src/test/fuzz/fuzz -max_total_time=1 >fuzz-0.log 2>&1
4================== Job 0 exited with exit code 0 ============
5Uninitialized bytes in fputs at offset 22 inside [0x72e000000000, 42177)
6==40315==WARNING: MemorySanitizer: use-of-uninitialized-value
7 [#0](/bitcoin-bitcoin/0/) 0x5640af00092f in Puts /msan/llvm-project/compiler-rt/lib/fuzzer/FuzzerIO.cpp:155:3
8 [#1](/bitcoin-bitcoin/1/) 0x5640af00092f in fuzzer::CopyFileToErr(std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>> const&) /msan/llvm-project/compiler-rt/lib/fuzzer/FuzzerIO.cpp:68:3
9 [#2](/bitcoin-bitcoin/2/) 0x5640aeff661c in fuzzer::WorkerThread(fuzzer::Command const&, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*) /msan/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:249:5
10 [#3](/bitcoin-bitcoin/3/) 0x5640aeff6991 in __invoke<void (*)(const fuzzer::Command &, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *> /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__type_traits/invoke.h:344:25
11 [#4](/bitcoin-bitcoin/4/) 0x5640aeff6991 in __thread_execute<std::__Fuzzer::unique_ptr<std::__Fuzzer::__thread_struct, std::__Fuzzer::default_delete<std::__Fuzzer::__thread_struct> >, void (*)(const fuzzer::Command &, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *, 2UL, 3UL, 4UL, 5UL> /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__thread/thread.h:193:3
12 [#5](/bitcoin-bitcoin/5/) 0x5640aeff6991 in void* std::__Fuzzer::__thread_proxy[abi:nn180100]<std::__Fuzzer::tuple<std::__Fuzzer::unique_ptr<std::__Fuzzer::__thread_struct, std::__Fuzzer::default_delete<std::__Fuzzer::__thread_struct>>, void (*)(fuzzer::Command const&, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*>>(void*) /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__thread/thread.h:202:3
13 [#6](/bitcoin-bitcoin/6/) 0x7f52f7e04a93 (/lib/x86_64-linux-gnu/libc.so.6+0x9ca93) (BuildId: 4d9090d61bf70e6b3225d583f0f08193f54670b2)
14 [#7](/bitcoin-bitcoin/7/) 0x7f52f7e91c3b (/lib/x86_64-linux-gnu/libc.so.6+0x129c3b) (BuildId: 4d9090d61bf70e6b3225d583f0f08193f54670b2)
15
16 Uninitialized value was stored to memory at
17 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
18 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
19
20 Uninitialized value was stored to memory at
21 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
22 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
23
24 Uninitialized value was stored to memory at
25 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
26 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
27
28 Uninitialized value was stored to memory at
29 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
30 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
31
32 Uninitialized value was stored to memory at
33 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
34 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
35
36 Uninitialized value was stored to memory at
37 [#0](/bitcoin-bitcoin/0/) 0x5640af0a8fbb in __msan_memmove /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1748:3
38 [#1](/bitcoin-bitcoin/1/) 0x5640af0311d9 in std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>>::push_back(char) cxa_noexception.cpp
39
40 Uninitialized value was created by a heap allocation
41 [#0](/bitcoin-bitcoin/0/) 0x5640af0b33c2 in malloc /msan/llvm-project/compiler-rt/lib/msan/msan_interceptors.cpp:1021:3
42 [#1](/bitcoin-bitcoin/1/) 0x5640b1b42203 in operator new(unsigned long) cxa_noexception.cpp
43 [#2](/bitcoin-bitcoin/2/) 0x5640af000913 in fuzzer::CopyFileToErr(std::__Fuzzer::basic_string<char, std::__Fuzzer::char_traits<char>, std::__Fuzzer::allocator<char>> const&) /msan/llvm-project/compiler-rt/lib/fuzzer/FuzzerIO.cpp:68:8
44 [#3](/bitcoin-bitcoin/3/) 0x5640aeff661c in fuzzer::WorkerThread(fuzzer::Command const&, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*) /msan/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:249:5
45 [#4](/bitcoin-bitcoin/4/) 0x5640aeff6991 in __invoke<void (*)(const fuzzer::Command &, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *> /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__type_traits/invoke.h:344:25
46 [#5](/bitcoin-bitcoin/5/) 0x5640aeff6991 in __thread_execute<std::__Fuzzer::unique_ptr<std::__Fuzzer::__thread_struct, std::__Fuzzer::default_delete<std::__Fuzzer::__thread_struct> >, void (*)(const fuzzer::Command &, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int> *, unsigned int, std::__Fuzzer::atomic<bool> *, 2UL, 3UL, 4UL, 5UL> /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__thread/thread.h:193:3
47 [#6](/bitcoin-bitcoin/6/) 0x5640aeff6991 in void* std::__Fuzzer::__thread_proxy[abi:nn180100]<std::__Fuzzer::tuple<std::__Fuzzer::unique_ptr<std::__Fuzzer::__thread_struct, std::__Fuzzer::default_delete<std::__Fuzzer::__thread_struct>>, void (*)(fuzzer::Command const&, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*), std::__Fuzzer::reference_wrapper<fuzzer::Command>, std::__Fuzzer::atomic<unsigned int>*, unsigned int, std::__Fuzzer::atomic<bool>*>>(void*) /msan/clang_build/runtimes/runtimes-bins/compiler-rt/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__thread/thread.h:202:3
48 [#7](/bitcoin-bitcoin/7/) 0x7f52f7e04a93 (/lib/x86_64-linux-gnu/libc.so.6+0x9ca93) (BuildId: 4d9090d61bf70e6b3225d583f0f08193f54670b2)
49
50SUMMARY: MemorySanitizer: use-of-uninitialized-value (/lib/x86_64-linux-gnu/libc.so.6+0x9ca93) (BuildId: 4d9090d61bf70e6b3225d583f0f08193f54670b2)
51Exiting