Interesting, that's potentially very good news! To be sure, could you try again with the latest code snippet? I forgot to remove the VM_PROT_EXECUTE flag for non-jailbroken devices.
Where does it crash? Try bumping the argument on line 21 – if you're unlucky library at index 1 contains mach_vm_read_overwrite and is suddenly no longer executable (since we change its second memory page from R-X to RW- due to stock kernels not allowing RWX pages).