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https://issues.apache.org/jira/browse/LUCENE-8720?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16841529#comment-16841529
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ASF subversion and git services commented on LUCENE-8720:
---------------------------------------------------------
Commit 5aff0a8937a9488bf985e1f81c96a1533dc3b085 in lucene-solr's branch
refs/heads/branch_7_7 from Jan Høydahl
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=5aff0a8 ]
LUCENE-8720: fix int overflow in NameIntCacheLRU
(Cherry picked from c9de94c66333fa3adfd0878ca6d38e05faff1738)
> Integer overflow bug in NameIntCacheLRU.makeRoomLRU()
> -----------------------------------------------------
>
> Key: LUCENE-8720
> URL: https://issues.apache.org/jira/browse/LUCENE-8720
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Affects Versions: 7.7.1
> Environment: Mac OS X 10.11.6 but this bug is not affected by the
> environment because it is a straightforward integer overflow bug.
> Reporter: Russell A Brown
> Priority: Major
> Labels: easyfix, patch
> Fix For: 7.7.2, 8.1, master (9.0)
>
> Attachments: LUCENE-NNNN.patch
>
>
> The NameIntCacheLRU.makeRoomLRU() method has an integer overflow bug because
> if maxCacheSize >= Integer.MAX_VALUE/2, 2*maxCacheSize will overflow to
> -(2^30) and the value of n will overflow to a negative integer as well, which
> will prevent any clearing of the cache whatsoever. Hence, performance will
> degrade once the cache becomes full because it will be impossible to remove
> any entries in order to add new entries to the cache.
> Moreover, comments in NameIntCacheLRU.java and LruTaxonomyWriterCache.java
> indicate that 2/3 of the cache will be cleared, whereas in fact only 1/3 of
> the cache is cleared. So as not to change the behavior of the
> NameIntCacheLRU.makeRoomLRU() method, I have not changed the code to clear
> 2/3 of the cache but instead I have changed the comments to indicate that 1/3
> of the cache is cleared.
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