pkg/report: don't record error for empty repro log case

It's not entirely normal, but it can still happen and it's not a big
problem by itself. Let's not pollute our error logs.

pkg/repro/repro.go

@@ -5,6 +5,7 @@ package repro
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"sort"
 	"sync"
@@ -59,14 +60,16 @@ type context struct {
 	timeouts     targets.Timeouts
 }
 
+var ErrNoPrograms = errors.New("crash log does not contain any programs")
+
 func Run(crashLog []byte, cfg *mgrconfig.Config, features *host.Features, reporter *report.Reporter,
 	vmPool *vm.Pool, vmIndexes []int) (*Result, *Stats, error) {
 	if len(vmIndexes) == 0 {
 		return nil, nil, fmt.Errorf("no VMs provided")
 	}
 	entries := cfg.Target.ParseLog(crashLog)
 	if len(entries) == 0 {
-		return nil, nil, fmt.Errorf("crash log does not contain any programs")
+		return nil, nil, ErrNoPrograms
 	}
 	crashStart := len(crashLog)
 	crashTitle, crashType := "", report.Unknown

syz-manager/manager.go

@@ -437,7 +437,7 @@ func (mgr *Manager) vmLoop() {
 			log.Logf(1, "loop: repro on %+v finished '%v', repro=%v crepro=%v desc='%v'",
 				res.instances, res.report0.Title, res.repro != nil, crepro, title)
 			if res.err != nil {
-				log.Errorf("repro failed: %v", res.err)
+				reportReproError(res.err)
 			}
 			delete(reproducing, res.report0.Title)
 			if res.repro == nil {
@@ -468,6 +468,17 @@ func (mgr *Manager) vmLoop() {
 	}
 }
 
+func reportReproError(err error) {
+	switch err {
+	case repro.ErrNoPrograms:
+		// This is not extraordinary as programs are collected via SSH.
+		log.Logf(0, "repro failed: %v", err)
+	default:
+		// Report everything else as errors.
+		log.Errorf("repro failed: %v", err)
+	}
+}
+
 func (mgr *Manager) runRepro(crash *Crash, vmIndexes []int, putInstances func(...int)) *ReproResult {
 	features := mgr.checkResult.Features
 	res, stats, err := repro.Run(crash.Output, mgr.cfg, features, mgr.reporter, mgr.vmPool, vmIndexes)