ruby: Unsafe use of alloca in rb_str_format()

The rbstrformat function in Ruby 1.8.4 and earlier, 1.8.5 before 1.8.5-p231, 1.8.6 before 1.8.6-p230, 1.8.7 before 1.8.7-p22, and 1.9.0 before 1.9.0-2 allows context-dependent attackers to trigger memory corruption via unspecified vectors related to alloca, a different issue than CVE-2008-2662,...