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Re: [PATCH v7 1/7] fuzz: accelerate non-crash detection
From: |
Alexander Bulekov |
Subject: |
Re: [PATCH v7 1/7] fuzz: accelerate non-crash detection |
Date: |
Sun, 10 Jan 2021 21:59:30 -0500 |
On 210110 2119, Qiuhao Li wrote:
> We spend much time waiting for the timeout program during the minimization
> process until it passes a time limit. This patch hacks the CLOSED (indicates
> the redirection file closed) notification in QTest's output if it doesn't
> crash.
>
> Test with quadrupled trace input at:
> https://bugs.launchpad.net/qemu/+bug/1890333/comments/1
>
> Original version:
> real 1m37.246s
> user 0m13.069s
> sys 0m8.399s
>
> Refined version:
> real 0m45.904s
> user 0m16.874s
> sys 0m10.042s
>
> Note:
>
> Sometimes the mutated or the same trace may trigger a different crash
> summary (second-to-last line) but indicates the same bug. For example, Bug
> 1910826 [1], which will trigger a stack overflow, may output summaries
> like:
>
> SUMMARY: AddressSanitizer: stack-overflow
> /home/qiuhao/hack/qemu/build/../softmmu/physmem.c:488 in
> flatview_do_translate
>
> or
>
> SUMMARY: AddressSanitizer: stack-overflow
> (/home/qiuhao/hack/qemu/build/qemu-system-i386+0x27ca049) in __asan_memcpy
>
> Etc.
>
> If we use the whole summary line as the token, we may be prevented from
> further minimization. So in this patch, we only use the first three words
> which indicate the type of crash:
>
> SUMMARY: AddressSanitizer: stack-overflow
>
> [1] https://bugs.launchpad.net/qemu/+bug/1910826
>
> Signed-off-by: Qiuhao Li <Qiuhao.Li@outlook.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Thanks
> ---
> scripts/oss-fuzz/minimize_qtest_trace.py | 43 +++++++++++++++++-------
> 1 file changed, 31 insertions(+), 12 deletions(-)
>
> diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py
> b/scripts/oss-fuzz/minimize_qtest_trace.py
> index 5e405a0d5f..97f1201747 100755
> --- a/scripts/oss-fuzz/minimize_qtest_trace.py
> +++ b/scripts/oss-fuzz/minimize_qtest_trace.py
> @@ -29,8 +29,14 @@ whether the crash occred. Optionally, manually set a
> string that idenitifes the
> crash by setting CRASH_TOKEN=
> """.format((sys.argv[0])))
>
> +deduplication_note = """\n\
> +Note: While trimming the input, sometimes the mutated trace triggers a
> different
> +type crash but indicates the same bug. Under this situation, our minimizer is
> +incapable of recognizing and stopped from removing it. In the future, we may
> +use a more sophisticated crash case deduplication method.
> +\n"""
> +
> def check_if_trace_crashes(trace, path):
> - global CRASH_TOKEN
> with open(path, "w") as tracefile:
> tracefile.write("".join(trace))
>
> @@ -41,18 +47,32 @@ def check_if_trace_crashes(trace, path):
> trace_path=path),
> shell=True,
> stdin=subprocess.PIPE,
> - stdout=subprocess.PIPE)
> - stdo = rc.communicate()[0]
> - output = stdo.decode('unicode_escape')
> - if rc.returncode == 137: # Timed Out
> - return False
> - if len(output.splitlines()) < 2:
> - return False
> -
> + stdout=subprocess.PIPE,
> + encoding="utf-8")
> + global CRASH_TOKEN
> if CRASH_TOKEN is None:
> - CRASH_TOKEN = output.splitlines()[-2]
> + try:
> + outs, _ = rc.communicate(timeout=5)
> + CRASH_TOKEN = " ".join(outs.splitlines()[-2].split()[0:3])
> + except subprocess.TimeoutExpired:
> + print("subprocess.TimeoutExpired")
> + return False
> + print("Identifying Crashes by this string: {}".format(CRASH_TOKEN))
> + global deduplication_note
> + print(deduplication_note)
> + return True
>
> - return CRASH_TOKEN in output
> + for line in iter(rc.stdout.readline, b''):
> + if "CLOSED" in line:
> + return False
> + if CRASH_TOKEN in line:
> + return True
> + # We reach the end of stdout and there is no "CLOSED" or CRASH_TOKEN
> + # Usually this is caused by a different type of crash
> + if line == "":
> + return False
> +
> + return False
>
>
> def minimize_trace(inpath, outpath):
> @@ -66,7 +86,6 @@ def minimize_trace(inpath, outpath):
> print("Crashed in {} seconds".format(end-start))
> TIMEOUT = (end-start)*5
> print("Setting the timeout for {} seconds".format(TIMEOUT))
> - print("Identifying Crashes by this string: {}".format(CRASH_TOKEN))
>
> i = 0
> newtrace = trace[:]
> --
> 2.25.1
>
- [PATCH v7 0/7] fuzz: improve crash case minimization, Qiuhao Li, 2021/01/10
- [PATCH v7 1/7] fuzz: accelerate non-crash detection, Qiuhao Li, 2021/01/10
- Re: [PATCH v7 1/7] fuzz: accelerate non-crash detection,
Alexander Bulekov <=
- [PATCH v7 2/7] fuzz: double the IOs to remove for every loop, Qiuhao Li, 2021/01/10
- [PATCH v7 4/7] fuzz: remove IO commands iteratively, Qiuhao Li, 2021/01/10
- [PATCH v7 3/7] fuzz: split write operand using binary approach, Qiuhao Li, 2021/01/10
- [PATCH v7 5/7] fuzz: set bits in operand of write/out to zero, Qiuhao Li, 2021/01/10
- [PATCH v7 6/7] fuzz: add minimization options, Qiuhao Li, 2021/01/10
- [PATCH v7 7/7] fuzz: heuristic split write based on past IOs, Qiuhao Li, 2021/01/10