pkg/report: ignore transient crashes

There are cases when a crash, even though it didn't occur during boot
and image testing phases, still should not be counted during bisection.
Otherwise we risk diverting the whole process in the wrong direction.

One of such problem classes is getting SYZFATAL errors when we are not
bisecting a SYZFATAL crash.

1 files changed, 17 insertions, 2 deletions

diff --git a/pkg/bisect/bisect.go b/pkg/bisect/bisect.go
index 3d3de92b6..9668144ef 100644
--- a/pkg/bisect/bisect.go
+++ b/pkg/bisect/bisect.go
@@ -698,14 +698,19 @@ func (env *env) processResults(current *vcs.Commit, results []instance.EnvTestRe
 			}
 			env.saveDebugFile(current.Hash, i, output)
 		case *instance.CrashError:
-			bad++
-			reports = append(reports, err.Report)
 			verdicts = append(verdicts, fmt.Sprintf("crashed: %v", err))
 			output := err.Report.Report
 			if len(output) == 0 {
 				output = err.Report.Output
 			}
 			env.saveDebugFile(current.Hash, i, output)
+			if env.isTransientError(err.Report) {
+				verdicts = append(verdicts, fmt.Sprintf("ignore: %v", err))
+				break
+			}
+			bad++
+			reports = append(reports, err.Report)
+			verdicts = append(verdicts, fmt.Sprintf("crashed: %v", err))
 		default:
 			infra++
 			verdicts = append(verdicts, fmt.Sprintf("failed: %v", err))
@@ -791,6 +796,16 @@ func mostFrequentReports(reports []*report.Report) (*report.Report, []crash.Type
 	return bestReport, bestTypes, len(bestTypes) != len(perType)
 }
 
+func (env *env) isTransientError(rep *report.Report) bool {
+	// If we're not chasing a SYZFATAL error, ignore them.
+	// Otherwise it indicates some transient problem of the tested kernel revision.
+	hadSyzFailure := false
+	for _, t := range env.reportTypes {
+		hadSyzFailure = hadSyzFailure || t == crash.SyzFailure
+	}
+	return rep.Type == crash.SyzFailure && !hadSyzFailure
+}
+
 func (env *env) saveDebugFile(hash string, idx int, data []byte) {
 	env.cfg.Trace.SaveFile(fmt.Sprintf("%v.%v", hash, idx), data)
 }