nodeJS too many child processes?

I am using node to recursively traverse a file system and make a system call for each file, by using child.exec. It works well when tested on a small structure, with a couple of folders and files, but when run on the whole home directory, it crashes after a while

child_process.js:945
throw errnoException(process._errno, 'spawn');
      ^
Error: spawn Unknown system errno 23
at errnoException (child_process.js:998:11)
at ChildProcess.spawn (child_process.js:945:11)
at exports.spawn (child_process.js:733:9)
at Object.exports.execFile (child_process.js:617:15)
at exports.exec (child_process.js:588:18)

Does this happen because it uses up all resources? How can I avoid this?

EDIT: Code improvement and best practices suggestions always welcome :)

    function processDir(dir, callback) {
        fs.readdir(dir, function (err, files) {
            if (err) {...}
            if (files) {
                async.each(files, function (file, cb) {
                        var filePath = dir + "/" + file;
                        var stats = fs.statSync(filePath);
                        if (stats) {
                            if (stats.isFile()) {
                                processFile(dir, file, function (err) {
                                    if (err) {...}
                                    cb();
                                });
                            } else if (stats.isDirectory()) {
                                processDir(filePath, function (err) {
                                    if (err) {...}
                                    cb();
                                });
                            }
                        }
                    }, function (err) {
                        if (err) {...}
                        callback();
                    }
                );
            }
        });
    }