fix: address review feedback for disk space check

- Add overflow guard for Bavail * Bsize multiplication (cap at MaxInt64)
- Handle negative values in formatBytes (return "0 B")
- Add edge case tests for Check (empty path, root dir, deeply nested)
- Add unit tests for estimateBuildSize (files, dirs, missing, empty)
- Fix copyright year to 2025 in new files

Signed-off-by: Zhao Chen <winters.zc@antgroup.com>

Author: aftersnow

pkg/backend/build_test.go

@@ -17,12 +17,14 @@
 package backend
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/modelpack/modctl/pkg/config"
 	"github.com/modelpack/modctl/test/mocks/modelfile"
-
-	"github.com/stretchr/testify/assert"
 )
 
 func TestGetProcessors(t *testing.T) {
@@ -41,3 +43,69 @@ func TestGetProcessors(t *testing.T) {
 	assert.Equal(t, "code", processors[2].Name())
 	assert.Equal(t, "doc", processors[3].Name())
 }
+
+func TestEstimateBuildSize(t *testing.T) {
+	t.Run("single files", func(t *testing.T) {
+		workDir := t.TempDir()
+
+		// Create test files with known sizes.
+		assert.NoError(t, os.WriteFile(filepath.Join(workDir, "model.bin"), make([]byte, 1024), 0644))
+		assert.NoError(t, os.WriteFile(filepath.Join(workDir, "config.json"), make([]byte, 256), 0644))
+
+		mf := &modelfile.Modelfile{}
+		mf.On("GetConfigs").Return([]string{"config.json"})
+		mf.On("GetModels").Return([]string{"model.bin"})
+		mf.On("GetCodes").Return([]string{})
+		mf.On("GetDocs").Return([]string{})
+
+		size := estimateBuildSize(workDir, mf)
+		assert.Equal(t, int64(1280), size)
+	})
+
+	t.Run("directory entry", func(t *testing.T) {
+		workDir := t.TempDir()
+
+		// Create a subdirectory with files.
+		subDir := filepath.Join(workDir, "models")
+		assert.NoError(t, os.MkdirAll(subDir, 0755))
+		assert.NoError(t, os.WriteFile(filepath.Join(subDir, "a.bin"), make([]byte, 512), 0644))
+		assert.NoError(t, os.WriteFile(filepath.Join(subDir, "b.bin"), make([]byte, 512), 0644))
+
+		mf := &modelfile.Modelfile{}
+		mf.On("GetConfigs").Return([]string{})
+		mf.On("GetModels").Return([]string{"models"})
+		mf.On("GetCodes").Return([]string{})
+		mf.On("GetDocs").Return([]string{})
+
+		size := estimateBuildSize(workDir, mf)
+		assert.Equal(t, int64(1024), size)
+	})
+
+	t.Run("nonexistent file is skipped", func(t *testing.T) {
+		workDir := t.TempDir()
+
+		assert.NoError(t, os.WriteFile(filepath.Join(workDir, "real.bin"), make([]byte, 100), 0644))
+
+		mf := &modelfile.Modelfile{}
+		mf.On("GetConfigs").Return([]string{})
+		mf.On("GetModels").Return([]string{"real.bin", "missing.bin"})
+		mf.On("GetCodes").Return([]string{})
+		mf.On("GetDocs").Return([]string{})
+
+		size := estimateBuildSize(workDir, mf)
+		assert.Equal(t, int64(100), size)
+	})
+
+	t.Run("empty modelfile", func(t *testing.T) {
+		workDir := t.TempDir()
+
+		mf := &modelfile.Modelfile{}
+		mf.On("GetConfigs").Return([]string{})
+		mf.On("GetModels").Return([]string{})
+		mf.On("GetCodes").Return([]string{})
+		mf.On("GetDocs").Return([]string{})
+
+		size := estimateBuildSize(workDir, mf)
+		assert.Equal(t, int64(0), size)
+	})
+}

pkg/diskspace/check.go

@@ -1,5 +1,5 @@
 /*
- *     Copyright 2024 The CNAI Authors
+ *     Copyright 2025 The CNAI Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@ package diskspace
 
 import (
 	"fmt"
+	"math"
 	"os"
 	"path/filepath"
 
@@ -59,7 +60,16 @@ func Check(dir string, requiredBytes int64) error {
 	}
 
 	// Available space for non-root users.
-	availableBytes := int64(stat.Bavail) * int64(stat.Bsize)
+	// Guard against overflow: on Linux Bavail is uint64, and values exceeding
+	// math.MaxInt64 would wrap negative when cast to int64. Cap at MaxInt64.
+	bavail := stat.Bavail
+	bsize := uint64(stat.Bsize)
+	var availableBytes int64
+	if bavail > 0 && bsize > uint64(math.MaxInt64)/bavail {
+		availableBytes = math.MaxInt64
+	} else {
+		availableBytes = int64(bavail * bsize)
+	}
 	requiredWithMargin := int64(float64(requiredBytes) * safetyMargin)
 
 	if availableBytes < requiredWithMargin {
@@ -74,6 +84,10 @@ func Check(dir string, requiredBytes int64) error {
 
 // formatBytes formats bytes into a human-readable string.
 func formatBytes(bytes int64) string {
+	if bytes < 0 {
+		return "0 B"
+	}
+
 	const (
 		kb = 1024
 		mb = kb * 1024

pkg/diskspace/check_test.go

@@ -1,5 +1,5 @@
 /*
- *     Copyright 2024 The CNAI Authors
+ *     Copyright 2025 The CNAI Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -62,11 +62,35 @@ func TestCheck_NonExistentDirWalksUp(t *testing.T) {
 	}
 }
 
+func TestCheck_EmptyPath(t *testing.T) {
+	// Empty string should walk up to root and succeed for small size
+	err := Check("", 1)
+	if err != nil {
+		t.Errorf("expected nil error for empty path with 1 byte, got: %v", err)
+	}
+}
+
+func TestCheck_RootDir(t *testing.T) {
+	err := Check("/", 1)
+	if err != nil {
+		t.Errorf("expected nil error for root dir with 1 byte, got: %v", err)
+	}
+}
+
+func TestCheck_DeeplyNestedNonExistentDir(t *testing.T) {
+	err := Check("/tmp/a/b/c/d/e/f/g/h", 1)
+	if err != nil {
+		t.Errorf("expected nil error for deeply nested non-existent path, got: %v", err)
+	}
+}
+
 func TestFormatBytes(t *testing.T) {
 	tests := []struct {
 		bytes    int64
 		expected string
 	}{
+		{-1, "0 B"},
+		{-1024, "0 B"},
 		{0, "0 B"},
 		{500, "500 B"},
 		{1024, "1.00 KB"},