[jira] Commented: (HADOOP-4271) Bug in FSInputChecker makes it possible to read from an invalid buffer

["Raghu Angadi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-4271?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634390#action_12634390 ] 

Raghu Angadi commented on HADOOP-4271:
--------------------------------------

Good catch. This can happen when {{seek()}} is used.  A few things:

- I think  (more) correct fix is to reset 'pos' and 'count' _before_ calling {{ readChecksumChunk()}}.. since once it is called, buffer is no longer valid (say there is some exception and user seeks again).

- You can generate 1500 bytes of random data in the test itself rather than requiring two extra files to be committed.

- Currently 'runTest()' fails only with checksum disabled. Same bug exists with checksum enabled as well, which is the common case. Can you change the test so that it fails with checksum enabled as well?

- There is already a {{TestFSInputChecksum.java}} in hdfs. Can you add this case there?

- Minor : using IOUtils.readFully() will reduce the code for the test. 

> Bug in FSInputChecker makes it possible to read from an invalid buffer
> ----------------------------------------------------------------------
>
>                 Key: HADOOP-4271
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4271
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: fs
>            Reporter: Ning Li
>            Priority: Minor
>         Attachments: .data_testFSInputChecker.crc, data_testFSInputChecker, hadoop-4271.patch
>
>
> Bug in FSInputChecker makes it possible to read from an invalid buffer. The buffer in FSInputChecker becomes invalid when readChecksumChunk is used to read a chunk to a user buffer directly. Currently, it's not marked as invalid in this case and may be read subsequently.

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