syz-cluster: consider multiple trees during triage

Even if the target tree is specified in the patch title, there happen to
be cases when it's actually only applicable to some other trees.

So instead of choosing one particular tree and sticking to it, obtain an
ordered list of candidates and pick the first to which the series
actually applies.

1 files changed, 53 insertions, 44 deletions

diff --git a/syz-cluster/workflow/triage-step/main.go b/syz-cluster/workflow/triage-step/main.go
index 9fa7a50bd..6aaeab84a 100644
--- a/syz-cluster/workflow/triage-step/main.go
+++ b/syz-cluster/workflow/triage-step/main.go
@@ -63,55 +63,64 @@ func getVerdict(ctx context.Context, tracer debugtracer.DebugTracer, client *api
 		// TODO: the workflow step must be retried.
 		return nil, fmt.Errorf("failed to query series: %w", err)
 	}
-	trees, err := client.GetTrees(ctx)
+	treesResp, err := client.GetTrees(ctx)
 	if err != nil {
 		return nil, fmt.Errorf("failed to query trees: %w", err)
 	}
-	tree := triage.SelectTree(series, trees.Trees)
-	if tree == nil {
+	selectedTrees := triage.SelectTrees(series, treesResp.Trees)
+	if len(selectedTrees) == 0 {
 		return &api.TriageResult{
-			SkipReason: "no suitable base kernel tree found",
+			SkipReason: "no suitable base kernel trees found",
 		}, nil
 	}
-	tracer.Log("selected tree %q", tree.Name)
-	arch := "amd64"
-	lastBuild, err := client.LastBuild(ctx, &api.LastBuildReq{
-		Arch:       arch,
-		ConfigName: tree.KernelConfig,
-		TreeName:   tree.Name,
-		Status:     api.BuildSuccess,
-	})
-	if err != nil {
-		// TODO: the workflow step must be retried.
-		return nil, fmt.Errorf("failed to query the last build: %w", err)
-	}
-	tracer.Log("last build: %q", lastBuild)
-	selector := triage.NewCommitSelector(ops, tracer)
-	result, err := selector.Select(series, tree, lastBuild)
-	if err != nil {
-		// TODO: the workflow step must be retried.
-		return nil, fmt.Errorf("failed to run the commit selector: %w", err)
-	} else if result.Commit == "" {
-		return &api.TriageResult{
-			SkipReason: "failed to find the base commit: " + result.Reason,
-		}, nil
-	}
-	tracer.Log("selected base commit: %s", result.Commit)
-	base := api.BuildRequest{
-		TreeName:   tree.Name,
-		TreeURL:    tree.URL,
-		ConfigName: tree.KernelConfig,
-		CommitHash: result.Commit,
-		Arch:       arch,
-	}
-	ret := &api.TriageResult{
-		Fuzz: &api.FuzzConfig{
-			Base:      base,
-			Patched:   base,
-			Config:    tree.FuzzConfig,
-			CorpusURL: tree.CorpusURL(),
-		},
+	var triageResult *api.TriageResult
+	for _, tree := range selectedTrees {
+		tracer.Log("considering tree %q", tree.Name)
+		arch := "amd64"
+		lastBuild, err := client.LastBuild(ctx, &api.LastBuildReq{
+			Arch:       arch,
+			ConfigName: tree.KernelConfig,
+			TreeName:   tree.Name,
+			Status:     api.BuildSuccess,
+		})
+		if err != nil {
+			// TODO: the workflow step must be retried.
+			return nil, fmt.Errorf("failed to query the last build for %q: %w", tree.Name, err)
+		}
+		tracer.Log("%q's last build: %q", tree.Name, lastBuild)
+		selector := triage.NewCommitSelector(ops, tracer)
+		result, err := selector.Select(series, tree, lastBuild)
+		if err != nil {
+			// TODO: the workflow step must be retried.
+			return nil, fmt.Errorf("failed to run the commit selector for %q: %w", tree.Name, err)
+		} else if result.Commit == "" {
+			// If we fail to find a suitable commit for all the trees, return an error just about the first one.
+			if triageResult == nil {
+				triageResult = &api.TriageResult{
+					SkipReason: "failed to find a base commit: " + result.Reason,
+				}
+			}
+			tracer.Log("failed to find a base commit for %q", tree.Name)
+			continue
+		}
+		tracer.Log("selected base commit: %s", result.Commit)
+		base := api.BuildRequest{
+			TreeName:   tree.Name,
+			TreeURL:    tree.URL,
+			ConfigName: tree.KernelConfig,
+			CommitHash: result.Commit,
+			Arch:       arch,
+		}
+		triageResult = &api.TriageResult{
+			Fuzz: &api.FuzzConfig{
+				Base:      base,
+				Patched:   base,
+				Config:    tree.FuzzConfig,
+				CorpusURL: tree.CorpusURL(),
+			},
+		}
+		triageResult.Fuzz.Patched.SeriesID = series.ID
+		break
 	}
-	ret.Fuzz.Patched.SeriesID = series.ID
-	return ret, nil
+	return triageResult, nil
 }