luzer: fix memory leak in FDP #66
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When luzer runs a test with broken dictionary it runs `LLVMFuzzerRunDriver()` that prints an error message: ParseDictionaryFile: error in line 1 "\\200\\000" # Uses: 283 the it frees argv[] and returns. A function `free_argv()` frees argv[] again and we observe a segmentation fault. The problem was fixed by the previous commit. The patch adds an additional test for the problem. Follows up #52 Closes #65
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Buristan
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Nov 10, 2025
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Sergey,
Thanks for the patch!
I suppose the next commit may be squashed into this one as well.
Please consider my comment below.
| LUA_SETHOOK(L, debug_hook, 0, 0); | ||
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| /* Prevents memory leaks on module exit. */ | ||
| lua_gc(L, LUA_GCCOLLECT, 0); |
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I suppose we have several smoking guns here:
- Since Lua (and therefore LuaJIT) has the GC-based memory management model, it may accumulate memory between iterations of state mutations in the TestOneInput. Libfuzzer checks the possible leaks during fuzzing between state mutations. Hence, we should add
-detect_leaks=0(see options) to the fuzzer options to be sure that we don't fail valid runs due to these false positives. This option disables only intermediate checks. The shutdown check is still enabled (but it may be ignored if you specify the environment variableLSAN_OPTIONS). Adding oflua_gc(), may not be so helpful if the object is allocated once at the first call (loading library viarequire) and cleared on the exit. - Even with the aforementioned option the
lua_close()isn't called since the process is finished by the atexit handler, which is set in theFuzzerDriver(). So, we will observe leaks of the FDP object allocated vianew.
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Also https://github.com/google/atheris/blob/master/native_extension_fuzzing.md#leak-detection
Leak detection
Python is known to leak certain data, such as at interpreter initialization time. You should disable leak detection, for example with -detect_leaks=0.
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Fixes #52