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From "Thomas Mueller (Jira)" <j...@apache.org>
Subject [jira] [Commented] (OAK-9095) MapRecord corruption when adding more than MapRecord.MAX_SIZE entries in branch record
Date Wed, 03 Jun 2020 15:23:00 GMT

    [ https://issues.apache.org/jira/browse/OAK-9095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17125049#comment-17125049

Thomas Mueller commented on OAK-9095:

[~adulceanu] +1 for the patch! It looks very good to me. (However, note that I'm not very
familiar with the segment store code, and I didn't test it. You might want to ask somebody
more familiar in this area to also review it.)

> MapRecord corruption when adding more than MapRecord.MAX_SIZE entries in branch record
> --------------------------------------------------------------------------------------
>                 Key: OAK-9095
>                 URL: https://issues.apache.org/jira/browse/OAK-9095
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: segment-tar
>    Affects Versions: 1.22.3, 1.8.22, 1.30.0
>            Reporter: Andrei Dulceanu
>            Assignee: Andrei Dulceanu
>            Priority: Major
>         Attachments: OAK-9095-02.patch, OAK-9095.patch
> It is now possible to write a {{MapRecord}} with a huge number of entries, going over
the maximum limit, {{MapRecord.MAX_SIZE}}, (i.e. 536.870.911 entries). This issue stems from
the fact that the number of entries is checked when writing a map leaf record [0], but not
when writing a map branch record [1]. When more than {{MapRecord.MAX_SIZE}} entries are written
in a branch record [2], the {{entrycCount}} overflows in the first bit of the level, essentially
rendering the entire HAMT structure corrupt, since the root branch record will be stored now
at level 1, instead of level 0, reporting an incorrect size as well (i.e. actual size - {{MapRecord.MAX_SIZE}}).
> Since this is a hard limit of the segment store and going above this number would mean
rewriting the internals of the HAMT structure currently in use, I propose the following mitigation:
> * add a size check for the branch record to not allow going over the limit
> * log a warning when the number of entries goes over 400.000.000
> * log an error when the number of entries goes over 500.000.000 and do not allow any
write operations on the node
> * allow further writes only if {{oak.segmentNodeStore.allowWritesOnHugeMapRecord}} system
property is present
> [0] https://github.com/apache/jackrabbit-oak/blob/1.22/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/DefaultSegmentWriter.java#L284
> [1] https://github.com/apache/jackrabbit-oak/blob/1.22/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/DefaultSegmentWriter.java#L291
> [2] https://github.com/apache/jackrabbit-oak/blob/1.22/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/RecordWriters.java#L231

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