Incorrect parsing of Libfuzzer flags

[forzafedor]

In the process of adding fuzzing flags, one of the flags was not parsed.

Example:

script lua:

local luzer = require("luzer")

local function TestOneInput(buf)
    local fdp = luzer.FuzzedDataProvider(buf)
    local str = fdp:consume_string(1)
    if str == "c" then
                assert(nil, "assert has triggered")
    end
    return
end

local opts = {
    --print_pcs = 1,
    --max_len = 4096,
    dd = 1,
    help = 1,
    print_pcs = 1,
}
luzer.Fuzz(TestOneInput, nil, opts)

Output log:

root@trixie:~/luzer/build/luzer# gdb /usr/bin/lua
GNU gdb (Debian 13.2-1) 13.2
Copyright (C) 2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Reading symbols from /usr/bin/lua...
Reading symbols from /usr/lib/debug/.build-id/97/c1063cf4058d17818dfa6325429bb6cdca9080.debug...
(gdb) run ../../luzer/tests/test_e2e.lua
Starting program: /usr/bin/lua ../../luzer/tests/test_e2e.lua
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

WARNING: unrecognized flag '-dd=1'; use -help=1 to list all flags

Usage:

To run fuzzing pass 0 or more directories.
-print_pcs=1 [-flag1=val1 [-flag2=val2 ...] ] [dir1 [dir2 ...] ]

To run individual tests without fuzzing pass 1 or more files:
-print_pcs=1 [-flag1=val1 [-flag2=val2 ...] ] file1 [file2 ...]

Flags: (strictly in form -flag=value)
 verbosity                              1       Verbosity level.
 seed                                   0       Random seed. If 0, seed is generated.
 runs                                   -1      Number of individual test runs (-1 for infinite runs).
 max_len                                0       Maximum length of the test input. If 0, libFuzzer tries to guess a good value based on the corpus and reports it.
 len_control                            100     Try generating small inputs first, then try larger inputs over time.  Specifies the rate at which the length limit is increased (smaller == faster).  If 0, immediately try inputs with size up to max_len. Default value is 0, if LLVMFuzzerCustomMutator is used.
 seed_inputs                            0       A comma-separated list of input files to use as an additional seed corpus. Alternatively, an "@" followed by the name of a file containing the comma-separated list.
 keep_seed                              0       If 1, keep seed inputs in the corpus even if they do not produce new coverage. When used with |reduce_inputs==1|, the seed inputs will never be reduced. This option can be useful when seeds arenot properly formed for the fuzz target but still have useful snippets.
 cross_over                             1       If 1, cross over inputs.
 cross_over_uniform_dist                0       Experimental. If 1, use a uniform probability distribution when choosing inputs to cross over with. Some of the inputs in the corpus may never get chosen for mutation depending on the input mutation scheduling policy. With this flag, all inputs, regardless of the input mutation scheduling policy, can be chosen as an input to cross over with. This can be particularly useful with |keep_seed==1|; all the initial seed inputs, even though they do not increase coverage because they are not properly formed, will still be chosen as an input to cross over with.
 mutate_depth                           5       Apply this number of consecutive mutations to each input.
 reduce_depth                           0       Experimental/internal. Reduce depth if mutations lose unique features
 shuffle                                1       Shuffle inputs at startup
 prefer_small                           1       If 1, always prefer smaller inputs during the corpus shuffle.
 timeout                                1200    Timeout in seconds (if positive). If one unit runs more than this number of seconds the process will abort.
 error_exitcode                         77      When libFuzzer itself reports a bug this exit code will be used.
 timeout_exitcode                       70      When libFuzzer reports a timeout this exit code will be used.
 max_total_time                         0       If positive, indicates the maximal total time in seconds to run the fuzzer.
 help                                   0       Print help.
 fork                                   0       Experimental mode where fuzzing happens in a subprocess
 fork_corpus_groups                     0       For fork mode, enable the corpus-group strategy, The main corpus will be grouped according to size, and each sub-process will randomly select seeds from different groups as the sub-corpus.
 ignore_timeouts                        1       Ignore timeouts in fork mode
 ignore_ooms                            1       Ignore OOMs in fork mode
 ignore_crashes                         0       Ignore crashes in fork mode
 merge                                  0       If 1, the 2-nd, 3-rd, etc corpora will be merged into the 1-st corpus. Only interesting units will be taken. This flag can be used to minimize a corpus.
 set_cover_merge                        0       If 1, the 2-nd, 3-rd, etc corpora will be merged into the 1-st corpus. Same as the 'merge' flag, but uses the standard greedy algorithm for the set cover problem to compute an approximation of the minimum set of testcases that provide the same coverage as the initial corpora
 stop_file                              0       Stop fuzzing ASAP if this file exists
 merge_control_file                     0       Specify a control file used for the merge process. If a merge process gets killed it tries to leave this file in a state suitable for resuming the merge. By default a temporary file will be used.The same file can be used for multistep merge process.
 minimize_crash                         0       If 1, minimizes the provided crash input. Use with -runs=N or -max_total_time=N to limit the number attempts. Use with -exact_artifact_path to specify the output. Combine with ASAN_OPTIONS=dedup_token_length=3 (or similar) to ensure that the minimized input triggers the same crash.
 cleanse_crash                          0       If 1, tries to cleanse the provided crash input to make it contain fewer original bytes. Use with -exact_artifact_path to specify the output.
 mutation_graph_file                    0       Saves a graph (in DOT format) to mutation_graph_file. The graph contains a vertex for each input that has unique coverage; directed edges are provided between parents and children where the child has unique coverage, and are recorded with the type of mutation that caused the child.
 use_counters                           1       Use coverage counters
 use_memmem                             1       Use hints from intercepting memmem, strstr, etc
 use_value_profile                      0       Experimental. Use value profile to guide fuzzing.
 use_cmp                                1       Use CMP traces to guide mutations
 shrink                                 0       Experimental. Try to shrink corpus inputs.
 reduce_inputs                          1       Try to reduce the size of inputs while preserving their full feature sets
 jobs                                   0       Number of jobs to run. If jobs >= 1 we spawn this number of jobs in separate worker processes with stdout/stderr redirected to fuzz-JOB.log.
 workers                                0       Number of simultaneous worker processes to run the jobs. If zero, "min(jobs,NumberOfCpuCores()/2)" is used.
 reload                                 1       Reload the main corpus every <N> seconds to get new units discovered by other processes. If 0, disabled
 report_slow_units                      10      Report slowest units if they run for more than this number of seconds.
 only_ascii                             0       If 1, generate only ASCII (isprint+isspace) inputs.
 dict                                   0       Experimental. Use the dictionary file.
 artifact_prefix                        0       Write fuzzing artifacts (crash, timeout, or slow inputs) as $(artifact_prefix)file
 exact_artifact_path                    0       Write the single artifact on failure (crash, timeout) as $(exact_artifact_path). This overrides -artifact_prefix and will not use checksum in the file name. Do not use the same path for several parallel processes.
 print_pcs                              0       If 1, print out newly covered PCs.
 print_funcs                            2       If >=1, print out at most this number of newly covered functions.
 print_final_stats                      0       If 1, print statistics at exit.
 print_corpus_stats                     0       If 1, print statistics on corpus elements at exit.
 print_coverage                         0       If 1, print coverage information as text at exit.
 print_full_coverage                    0       If 1, print full coverage information (all branches) as text at exit.
 dump_coverage                          0       Deprecated.
 handle_segv                            1       If 1, try to intercept SIGSEGV.
 handle_bus                             1       If 1, try to intercept SIGBUS.
 handle_abrt                            1       If 1, try to intercept SIGABRT.
 handle_ill                             1       If 1, try to intercept SIGILL.
 handle_fpe                             1       If 1, try to intercept SIGFPE.
 handle_int                             1       If 1, try to intercept SIGINT.
 handle_term                            1       If 1, try to intercept SIGTERM.
 handle_xfsz                            1       If 1, try to intercept SIGXFSZ.
 handle_usr1                            1       If 1, try to intercept SIGUSR1.
 handle_usr2                            1       If 1, try to intercept SIGUSR2.
 handle_winexcept                       1       If 1, try to intercept uncaught Windows Visual C++ Exceptions.
 close_fd_mask                          0       If 1, close stdout at startup; if 2, close stderr; if 3, close both. Be careful, this will also close e.g. stderr of asan.
 detect_leaks                           1       If 1, and if LeakSanitizer is enabled try to detect memory leaks during fuzzing (i.e. not only at shut down).
 purge_allocator_interval               1       Purge allocator caches and quarantines every <N> seconds. When rss_limit_mb is specified (>0), purging starts when RSS exceeds 50% of rss_limit_mb. Pass purge_allocator_interval=-1 to disable this functionality.
 trace_malloc                           0       If >= 1 will print all mallocs/frees. If >= 2 will also print stack traces.
 rss_limit_mb                           2048    If non-zero, the fuzzer will exit uponreaching this limit of RSS memory usage.
 malloc_limit_mb                        0       If non-zero, the fuzzer will exit if the target tries to allocate this number of Mb with one malloc call. If zero (default) same limit as rss_limit_mb is applied.
 exit_on_src_pos                        0       Exit if a newly found PC originates from the given source location. Example: -exit_on_src_pos=foo.cc:123. Used primarily for testing libFuzzer itself.
 exit_on_item                           0       Exit if an item with a given sha1 sum was added to the corpus. Used primarily for testing libFuzzer itself.
 ignore_remaining_args                  0       If 1, ignore all arguments passed after this one. Useful for fuzzers that need to do their own argument parsing.
 focus_function                         0       Experimental. Fuzzing will focus on inputs that trigger calls to this function. If -focus_function=auto and -data_flow_trace is used, libFuzzer will choose the focus functions automatically. Disables -entropic when specified.
 entropic                               1       Enables entropic power schedule.
 entropic_feature_frequency_threshold   255     Experimental. If entropic is enabled, all features which are observed less often than the specified value are considered as rare.
 entropic_number_of_rarest_features     100     Experimental. If entropic is enabled, we keep track of the frequencies only for the Top-X least abundant features (union features that are considered as rare).
 entropic_scale_per_exec_time           0       Experimental. If 1, the Entropic power schedule gets scaled based on the input execution time. Inputs with lower execution time get scheduled more (up to 30x). Note that, if 1, fuzzer stops from being deterministic even if a non-zero random seed is given.
 analyze_dict                           0       Experimental
 use_clang_coverage                     0       Deprecated; don't use
 data_flow_trace                        0       Experimental: use the data flow trace
 collect_data_flow                      0       Experimental: collect the data flow trace
 create_missing_dirs                    0       Automatically attempt to create directories for arguments that would normally expect them to already exist (i.e. artifact_prefix, exact_artifact_path, features_dir, corpus)

Flags starting with '--' will be ignored and will be passed verbatim to subprocesses.
free(): invalid pointer

Program received signal SIGABRT, Aborted.
__pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at ./nptl/pthread_kill.c:44
44      ./nptl/pthread_kill.c: No such file or directory.
(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at ./nptl/pthread_kill.c:44
#1  0x00007ffff7d2915f in __pthread_kill_internal (signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:78
#2  0x00007ffff7cdb472 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3  0x00007ffff7cc54b2 in __GI_abort () at ./stdlib/abort.c:79
#4  0x00007ffff7cc61ed in __libc_message (fmt=fmt@entry=0x7ffff7e3878c "%s\n") at ../sysdeps/posix/libc_fatal.c:150
#5  0x00007ffff7d32a75 in malloc_printerr (str=str@entry=0x7ffff7e3622c "free(): invalid pointer") at ./malloc/malloc.c:5658
#6  0x00007ffff7d347f4 in _int_free (av=<optimized out>, p=<optimized out>, have_lock=have_lock@entry=0) at ./malloc/malloc.c:4432
#7  0x00007ffff7d3716f in __GI___libc_free (mem=<optimized out>) at ./malloc/malloc.c:3367
#8  0x000055555556c119 in l_alloc (ud=<optimized out>, ptr=<optimized out>, osize=<optimized out>, nsize=<optimized out>) at ./src/lauxlib.c:631
#9  0x000055555556373e in luaM_realloc_ (L=L@entry=0x5555555872a0, block=<optimized out>, osize=16, nsize=nsize@entry=0) at ./src/lmem.c:79
#10 0x00005555555680df in luaH_free (L=L@entry=0x5555555872a0, t=t@entry=0x5555555911c0) at ./src/ltable.c:377
#11 0x00005555555625db in freeobj (o=0x5555555911c0, L=0x5555555872a0) at ./src/lgc.c:383
#12 sweeplist (L=L@entry=0x5555555872a0, p=p@entry=0x555555587380, count=18446744073709551601, count@entry=18446744073709551613) at ./src/lgc.c:424
#13 0x000055555556343f in luaC_freeall (L=L@entry=0x5555555872a0) at ./src/lgc.c:487
#14 0x00005555555673be in close_state (L=0x5555555872a0) at ./src/lstate.c:108
#15 0x0000555555567899 in lua_close (L=<optimized out>) at ./src/lstate.c:212
#16 0x000055555555a6f6 in main (argc=2, argv=0x7fffffffecf8) at ./src/lua.c:389

Problems:

1. Incorrect output for help flag: Result in script: -print_pcs=1 [-flag1=val1 [-flag2=val2 ...] ] [dir1 [dir2 ...] ] Expected result: ../../examples/example_basic.lua [-flag1=val1 [-flag2=val2 ...] ] [dir1 [dir2 ...] ] Script processed the first flag as name of program file
2. Incorrect ending fuzz process: Result in script:

   
   free(): invalid pointer

Program received signal SIGABRT, Aborted.

[forzafedor]

Solved the problem in PR #14.

I don’t know how good the solution is, but the problem with flags is solved and now one can add flags from console. But the algorithm for passing parameters at the Lua level has changed.