tests: add a fuzzer for catalog_import_file

[evverx]

No description provided.

[evverx]

The fuzzer has found a place where an assertion is used to check whether the input is valid, which means that it's going to crash with

==12==ERROR: AddressSanitizer: ABRT on unknown address 0x00000000000c (pc 0x7fd6d4788428 bp 0x7fffad5fe1d0 sp 0x7fffad5fe068 T0)
SCARINESS: 10 (signal)
    #0 0x7fd6d4788427 in gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x35427)
    #1 0x7fd6d478a029 in abort (/lib/x86_64-linux-gnu/libc.so.6+0x37029)
    #2 0x7fd6d5a2aeaa in log_assert_failed_realm /work/build/../../src/systemd/src/basic/log.c:795:9
    #3 0x7fd6d5bb6d47 in finish_item /work/build/../../src/systemd/src/journal/catalog.c:164:17
    #4 0x7fd6d5bb5f74 in catalog_import_file /work/build/../../src/systemd/src/journal/catalog.c:313:45
    #5 0x530a89 in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-catalog.c:23:16
    #6 0x55be35 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:571:15
    #7 0x559d07 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:480:3
    #8 0x55db12 in fuzzer::Fuzzer::MutateAndTestOne() /src/libfuzzer/FuzzerLoop.cpp:708:19
    #9 0x560aa6 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:839:5
    #10 0x53dc21 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:764:6
    #11 0x530cdc in main /src/libfuzzer/FuzzerMain.cpp:20:10
    #12 0x7fd6d477382f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #13 0x41d078 in _start (/out/fuzz-catalog+0x41d078)

but it can be fixed later in a separate PR.

[keszybz]

Ubuntu CI does not checks the fuzzers (except running them on the corpus), so let's merge without waiting.

[evverx]

As far as I know, nobody has added -Dslow-tests to debian/rules so Ubuntu CI doesn't even try to compile the fuzzers.