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https://issues.apache.org/jira/browse/OAK-9095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17125705#comment-17125705
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Andrei Dulceanu commented on OAK-9095:
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Backported to 1.22 branch at r1878468.
> 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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