diff mbox series

[v2,4/7] fuzz: loop the remove minimizer and refactoring

Message ID ME3P282MB17455626AA33AA43881D4CA0FCD90@ME3P282MB1745.AUSP282.PROD.OUTLOOK.COM (mailing list archive)
State New, archived
Headers show
Series fuzz: improve crash case minimization | expand

Commit Message

Qiuhao Li Dec. 28, 2020, 5:56 a.m. UTC
Now we use a one-time scan and remove strategy in the remval minimizer,
which is not suitable for timing dependent instructions.

For example, instruction A will indicate an address where the config
chunk locates, and instruction B will make the configuration active. If
we have the following instruction sequence:

...
A1
B1
A2
B2
...

A2 and B2 are the actual instructions that trigger the bug.

If we scan from top to bottom, after we remove A1, the behavior of B1
might be unknowable, including not to crash the program. But we will
successfully remove B1 later cause A2 and B2 will crash the process
anyway:

...
A1
A2
B2
...

Now one more trimming will remove A1.

In the perfect case, we would need to be able to remove A and B (or C!) at
the same time. But for now, let's just add a loop around the minimizer.

Since we only remove instructions, this iterative algorithm is converging.

Tested with Bug 1908062.

Signed-off-by: Qiuhao Li <Qiuhao.Li@outlook.com>
---
 scripts/oss-fuzz/minimize_qtest_trace.py | 41 +++++++++++++++---------
 1 file changed, 26 insertions(+), 15 deletions(-)
diff mbox series

Patch

diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py b/scripts/oss-fuzz/minimize_qtest_trace.py
index dd6eeb7258..0cc88da933 100755
--- a/scripts/oss-fuzz/minimize_qtest_trace.py
+++ b/scripts/oss-fuzz/minimize_qtest_trace.py
@@ -71,21 +71,9 @@  def check_if_trace_crashes(trace, path):
     return False
 
 
-def minimize_trace(inpath, outpath):
-    global TIMEOUT
-    with open(inpath) as f:
-        trace = f.readlines()
-    start = time.time()
-    if not check_if_trace_crashes(trace, outpath):
-        sys.exit("The input qtest trace didn't cause a crash...")
-    end = time.time()
-    print("Crashed in {} seconds".format(end-start))
-    TIMEOUT = (end-start)*5
-    print("Setting the timeout for {} seconds".format(TIMEOUT))
-
-    i = 0
-    newtrace = trace[:]
+def remove_minimizer(newtrace, outpath):
     remove_step = 1
+    i = 0
     while i < len(newtrace):
         # 1.) Try to remove lines completely and reproduce the crash.
         # If it works, we're done.
@@ -174,7 +162,30 @@  def minimize_trace(inpath, outpath):
                     newtrace[i] = prior[0]
                     del newtrace[i+1]
         i += 1
-    check_if_trace_crashes(newtrace, outpath)
+
+
+def minimize_trace(inpath, outpath):
+    global TIMEOUT
+    with open(inpath) as f:
+        trace = f.readlines()
+    start = time.time()
+    if not check_if_trace_crashes(trace, outpath):
+        sys.exit("The input qtest trace didn't cause a crash...")
+    end = time.time()
+    print("Crashed in {} seconds".format(end-start))
+    TIMEOUT = (end-start)*5
+    print("Setting the timeout for {} seconds".format(TIMEOUT))
+
+    newtrace = trace[:]
+
+    # remove minimizer
+    old_len = len(newtrace) + 1
+    while(old_len > len(newtrace)):
+        old_len = len(newtrace)
+        remove_minimizer(newtrace, outpath)
+        newtrace = list(filter(lambda s: s != "", newtrace))
+    
+    assert(check_if_trace_crashes(newtrace, outpath))
 
 
 if __name__ == '__main__':