Help assessing Ruby fix to yaml

Hello,

As of version 2.0.0, Ruby carries a vendored copy of yaml in
"ext/psych/yaml".  Yesterday they went to yaml version 0.1.5.

However, an additional fix was introduced to the trunk branch which
claims to address a potential integer overflow. The fix is here:
https://github.com/ruby/ruby/commit/cb7e80682977f78bfcb2b9e92695e3420b8fd98d.

I'm trying to determine if that diff represents a fix to a potential
security vulnerability, but I'm afraid my familiarity with the yaml
source code is not very good.

Does this appear to be a security vulnerability? I'm trying to
determine if I need to pull this patch in.

Thank you for your help.

-- 
Moses Mendoza
Puppet Labs

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