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https://issues.apache.org/jira/browse/LUCENE-8720?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Russell A Brown updated LUCENE-8720:
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Description:
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.
was:
The NameIntCacheLRU.makeRoomLRU() method has an integer overflow bug because if
maxCacheSize >= Integer.MAX_VALUE/2, 2*maxCacheSize will overflow to -65536 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.
> 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: 7.1.1
>
> 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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