Ruby memory corruption in BigDecimal on 64bit platforms

The VpMemAlloc function in bigdecimal.c in the BigDecimal class in Ruby
1.9.2-p136 and earlier, as used on Apple Mac OS X before 10.6.7 and other
platforms, does not properly allocate memory, which allows context-dependent
attackers to execute arbitrary code or cause a denial of service (application
crash) via vectors involving creation of a large BigDecimal value within a
64-bit process, related to an “integer truncation issue.”