fuzz: accelerate non-crash detection
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>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <SYCPR01MB350251DC04003450348FAF68FCAB0@SYCPR01MB3502.ausprd01.prod.outlook.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py b/scripts/oss-fuzz/minimize_qtest_trace.py
index 5e405a0..a28913a 100755
--- a/scripts/oss-fuzz/minimize_qtest_trace.py
+++ b/scripts/oss-fuzz/minimize_qtest_trace.py
@@ -29,8 +29,14 @@
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 +47,31 @@
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, ""):
+ if "CLOSED" in line:
+ return False
+ if CRASH_TOKEN in line:
+ return True
+
+ print("\nWarning:")
+ print(" There is no 'CLOSED'or CRASH_TOKEN in the stdout of subprocess.")
+ print(" Usually this indicates a different type of crash.\n")
+ return False
def minimize_trace(inpath, outpath):
@@ -66,7 +85,6 @@
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[:]
