add path overlap protection

Author: taigrr

internal/cmd/mount.go

@@ -5,6 +5,8 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"path/filepath"
+	"strings"
 
 	"bazil.org/fuse"
 	"bazil.org/fuse/fs"
@@ -29,13 +31,45 @@ MOUNTPOINT is the directory where the filesystem will be mounted.`,
 	}
 }
 
+// pathsOverlap checks if two paths overlap (one contains the other).
+// It returns true if either path is a parent/child of the other.
+func pathsOverlap(path1, path2 string) bool {
+	// Convert to absolute paths and clean them
+	abs1, err1 := filepath.Abs(path1)
+	abs2, err2 := filepath.Abs(path2)
+	
+	// If we can't resolve absolute paths, compare as-is
+	if err1 != nil {
+		abs1 = filepath.Clean(path1)
+	}
+	if err2 != nil {
+		abs2 = filepath.Clean(path2)
+	}
+	
+	// Ensure paths end with separator for accurate prefix checking
+	if !strings.HasSuffix(abs1, string(filepath.Separator)) {
+		abs1 += string(filepath.Separator)
+	}
+	if !strings.HasSuffix(abs2, string(filepath.Separator)) {
+		abs2 += string(filepath.Separator)
+	}
+	
+	// Check if either path is a prefix of the other
+	return strings.HasPrefix(abs1, abs2) || strings.HasPrefix(abs2, abs1)
+}
+
 func runMount(cmd *cobra.Command, args []string) {
 	// Print version info on startup
 	fmt.Printf("djafs %s starting...\n", version.GetFullVersion())
 
 	storagePath := args[0]
 	mountpoint := args[1]
 
+	// Validate that storage path and mountpoint don't overlap
+	if pathsOverlap(storagePath, mountpoint) {
+		log.Fatalf("Storage path and mountpoint cannot overlap: storage=%s, mount=%s", storagePath, mountpoint)
+	}
+
 	// Ensure storage directory exists
 	if err := os.MkdirAll(storagePath, 0755); err != nil {
 		log.Fatalf("Failed to create storage directory: %v", err)

internal/cmd/mount_test.go

@@ -0,0 +1,66 @@
+package cmd
+
+import (
+	"testing"
+)
+
+func TestPathsOverlap(t *testing.T) {
+	tests := []struct {
+		name     string
+		path1    string
+		path2    string
+		expected bool
+	}{
+		{
+			name:     "identical paths",
+			path1:    "/tmp/storage",
+			path2:    "/tmp/storage",
+			expected: true,
+		},
+		{
+			name:     "path1 contains path2",
+			path1:    "/tmp/storage/data",
+			path2:    "/tmp/storage",
+			expected: true,
+		},
+		{
+			name:     "path2 contains path1",
+			path1:    "/tmp/storage",
+			path2:    "/tmp/storage/mount",
+			expected: true,
+		},
+		{
+			name:     "completely separate paths",
+			path1:    "/tmp/storage",
+			path2:    "/mnt/mount",
+			expected: false,
+		},
+		{
+			name:     "sibling directories",
+			path1:    "/tmp/storage",
+			path2:    "/tmp/mount",
+			expected: false,
+		},
+		{
+			name:     "relative paths - overlapping",
+			path1:    "storage",
+			path2:    "storage/mount",
+			expected: true,
+		},
+		{
+			name:     "relative paths - separate",
+			path1:    "storage",
+			path2:    "mount",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := pathsOverlap(tt.path1, tt.path2)
+			if result != tt.expected {
+				t.Errorf("pathsOverlap(%q, %q) = %v, expected %v", tt.path1, tt.path2, result, tt.expected)
+			}
+		})
+	}
+}