fix: convert Go FileMode to Unix mode_t for FUSE attributes

Go's os.FileMode uses a different bit layout than Unix mode_t:
ModeDir is 1<<31 in Go but S_IFDIR is 0040000 in Unix. When
populating fuse.Attr.Mode, the raw uint32 cast preserved Go's
layout, causing FUSE to see directories as regular files.

Added goModeToUnix() that properly maps all Go file type bits
(dir, symlink, pipe, socket, device) and special bits (setuid,
setgid, sticky) to their Unix/syscall equivalents.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: yasithdev

subsystems/mount/overlayfs.go

@@ -342,8 +342,42 @@ func (n *overlayNode) locateChild(name string) source {
 	}
 }
 
+// goModeToUnix converts Go's os.FileMode to a Unix mode_t (uint32).
+// Go uses its own bit layout (e.g. ModeDir = 1<<31) which differs from
+// Unix/FUSE mode bits (S_IFDIR = 0040000). This must be used whenever
+// populating fuse.Attr.Mode, fuse.DirEntry.Mode, or fs.StableAttr.Mode.
+func goModeToUnix(m os.FileMode) uint32 {
+	perm := uint32(m.Perm())
+	switch {
+	case m.IsDir():
+		perm |= syscall.S_IFDIR
+	case m&os.ModeSymlink != 0:
+		perm |= syscall.S_IFLNK
+	case m&os.ModeNamedPipe != 0:
+		perm |= syscall.S_IFIFO
+	case m&os.ModeSocket != 0:
+		perm |= syscall.S_IFSOCK
+	case m&os.ModeCharDevice != 0:
+		perm |= syscall.S_IFCHR
+	case m&os.ModeDevice != 0:
+		perm |= syscall.S_IFBLK
+	default:
+		perm |= syscall.S_IFREG
+	}
+	if m&os.ModeSetuid != 0 {
+		perm |= syscall.S_ISUID
+	}
+	if m&os.ModeSetgid != 0 {
+		perm |= syscall.S_ISGID
+	}
+	if m&os.ModeSticky != 0 {
+		perm |= syscall.S_ISVTX
+	}
+	return perm
+}
+
 func localAttrToFuse(info os.FileInfo, out *fuse.Attr) {
-	out.Mode = uint32(info.Mode())
+	out.Mode = goModeToUnix(info.Mode())
 	out.Size = uint64(info.Size())
 	out.Mtime = uint64(info.ModTime().Unix())
 	fillStatFields(info, out)
@@ -352,14 +386,14 @@ func localAttrToFuse(info os.FileInfo, out *fuse.Attr) {
 func sftpAttrToFuse(info os.FileInfo, out *fuse.Attr) {
 	s := info.Sys()
 	if stat, ok := s.(*sftp.FileStat); ok {
-		out.Mode = uint32(info.Mode())
+		out.Mode = goModeToUnix(info.Mode())
 		out.Size = uint64(info.Size())
 		out.Mtime = uint64(stat.Mtime)
 		out.Atime = uint64(stat.Atime)
 		out.Uid = stat.UID
 		out.Gid = stat.GID
 	} else {
-		out.Mode = uint32(info.Mode())
+		out.Mode = goModeToUnix(info.Mode())
 		out.Size = uint64(info.Size())
 		out.Mtime = uint64(info.ModTime().Unix())
 		out.Atime = out.Mtime
@@ -387,13 +421,13 @@ func (n *overlayNode) Lookup(ctx context.Context, name string, out *fuse.EntryOu
 	// Check upper first
 	if info, err := os.Lstat(up); err == nil {
 		localAttrToFuse(info, &out.Attr)
-		stable := fs.StableAttr{Mode: uint32(info.Mode())}
+		stable := fs.StableAttr{Mode: goModeToUnix(info.Mode())}
 		return n.NewInode(ctx, child, stable), fs.OK
 	}
 	// Fall back to lower
 	if info, err := n.sftpLstat(rp); err == nil {
 		sftpAttrToFuse(info, &out.Attr)
-		stable := fs.StableAttr{Mode: uint32(info.Mode())}
+		stable := fs.StableAttr{Mode: goModeToUnix(info.Mode())}
 		return n.NewInode(ctx, child, stable), fs.OK
 	}
 	return nil, syscall.ENOENT
@@ -413,7 +447,7 @@ func (n *overlayNode) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno)
 			seen[e.Name()] = struct{}{}
 			result = append(result, fuse.DirEntry{
 				Name: e.Name(),
-				Mode: uint32(info.Mode()),
+				Mode: goModeToUnix(info.Mode()),
 			})
 		}
 	}
@@ -431,7 +465,7 @@ func (n *overlayNode) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno)
 			}
 			result = append(result, fuse.DirEntry{
 				Name: e.Name(),
-				Mode: uint32(e.Mode()),
+				Mode: goModeToUnix(e.Mode()),
 			})
 		}
 		return nil
@@ -563,7 +597,7 @@ func (n *overlayNode) Create(ctx context.Context, name string, flags uint32, mod
 	localAttrToFuse(info, &out.Attr)
 
 	child := n.child(name)
-	stable := fs.StableAttr{Mode: uint32(info.Mode())}
+	stable := fs.StableAttr{Mode: goModeToUnix(info.Mode())}
 	inode := n.NewInode(ctx, child, stable)
 	return inode, &localFileHandle{f: f}, fuse.FOPEN_DIRECT_IO, fs.OK
 }
@@ -581,7 +615,7 @@ func (n *overlayNode) Mkdir(ctx context.Context, name string, mode uint32, out *
 	localAttrToFuse(info, &out.Attr)
 
 	child := n.child(name)
-	stable := fs.StableAttr{Mode: uint32(info.Mode())}
+	stable := fs.StableAttr{Mode: goModeToUnix(info.Mode())}
 	return n.NewInode(ctx, child, stable), fs.OK
 }
 
@@ -684,7 +718,7 @@ func (n *overlayNode) Symlink(ctx context.Context, target, name string, out *fus
 	localAttrToFuse(info, &out.Attr)
 
 	child := n.child(name)
-	stable := fs.StableAttr{Mode: uint32(info.Mode())}
+	stable := fs.StableAttr{Mode: goModeToUnix(info.Mode())}
 	return n.NewInode(ctx, child, stable), fs.OK
 }