[jira] Closed: (DERBY-3739) Skip and read methods in ArrayInputStream may overflow

["Knut Anders Hatlen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-3739?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Knut Anders Hatlen closed DERBY-3739.
-------------------------------------

       Resolution: Fixed
    Fix Version/s: 10.5.0.0

Committed revision 673610.

> Skip and read methods in ArrayInputStream may overflow
> ------------------------------------------------------
>
>                 Key: DERBY-3739
>                 URL: https://issues.apache.org/jira/browse/DERBY-3739
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.5.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>             Fix For: 10.5.0.0
>
>         Attachments: d3739-read.diff, d3739-skip.diff, d3739-skip.stat, ReadOverflow.java
>
>
> If ArrayInputStream.skip() is called with a large value (like Long.MAX_VALUE) an internal calculation may overflow and cause unexpected results.
> It's the line which says
>     if ((position + count) > end) {
> that can overflow. If count (a long) is so big that position + count doesn't fit in a long, the condition will evaluate to false although it should have evaluated to true. Changing the condition to (count > end - position) will fix the problem. Alternatively, we could simplify the entire method body to:
>     count = Math.min(count, end - position);
>     position += count;
>     return count;

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