HDFS-11719. Arrays.fill() wrong index in BlockSender.readChecksum() exception handling. Contributed by Tao Zhang

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java

@@ -682,16 +682,17 @@ private void readChecksum(byte[] buf, final int checksumOffset,
           + " at offset " + offset + " for block " + block, e);
       ris.closeChecksumStream();
       if (corruptChecksumOk) {
-        if (checksumOffset < checksumLen) {
+        if (checksumLen > 0) {
           // Just fill the array with zeros.
-          Arrays.fill(buf, checksumOffset, checksumLen, (byte) 0);
+          Arrays.fill(buf, checksumOffset, checksumOffset + checksumLen,
+              (byte) 0);
         }
       } else {
         throw e;
       }
     }
   }
-  
+
   /**
    * Compute checksum for chunks and verify the checksum that is read from
    * the metadata file is correct.