libriscv: Out of bounds read vuln in the ELF parser (Denial of service)

libriscv is a RISC-V sandbox and emulator. Prior to 1.18, a crafted ELF binary can cause out-of-bounds reads in the host emulator. Memory<W>::binary_loader checks PT_LOAD program-header bounds, but Memory<W>::serialize_execute_segment trusts section-header sh_offset and sh_size when locating .text without verifying the file range against m_binary.size(); Memory<W>::lookup() has a similar section-table problem. Malformed .text or .symtab offsets can therefore bypass the program-header checks and point outside the binary buffer, crashing rvlinux. With suitable memory layout or integer overflow, out-of-buffer host heap memory may instead be mapped into the guest by create_execute_segment(), potentially exposing host memory. The reported reproducer demonstrates a host SIGSEGV, while memory disclosure through grooming is described as possible rather than demonstrated. This issue is fixed in version 1.18.