Scan text in 64KB chunks

This commit fixes a potential denial of service
vulnerability in logrus.Writer() that could be
triggered by logging text longer than 64KB
without newlines. Previously, the bufio.Scanner
used by Writer() would hang indefinitely when
reading such text without newlines, causing the
application to become unresponsive.

writer.go

@@ -75,7 +75,8 @@ func (entry *Entry) writerScanner(reader *io.PipeReader, printFunc func(args ...
 		if len(data) > chunkSize {
 			return chunkSize, data[:chunkSize], nil
 		}
-		return 0, nil, nil
+
+		return len(data), data, nil
 	}
 
 	//Use the custom split function to split the input