Merge "Fix ubsan error path found by libfstab_fuzzer"

            if (auto equal_sign = flag.find('='); equal_sign != std::string::npos) {

                const auto arg = flag.substr(equal_sign + 1);

                if (entry->fs_type == "f2fs" && StartsWith(flag, "reserve_root=")) {

                    if (!ParseInt(arg, &entry->reserved_size)) {

                    off64_t size_in_4k_blocks;

                    if (!ParseInt(arg, &size_in_4k_blocks, static_cast<off64_t>(0),

                                  std::numeric_limits<off64_t>::max() >> 12)) {

                        LWARNING << "Warning: reserve_root= flag malformed: " << arg;

                    } else {

                        entry->reserved_size <<= 12;

                        entry->reserved_size = size_in_4k_blocks << 12;

                    }

                } else if (StartsWith(flag, "lowerdir=")) {

                    entry->lowerdir = std::move(arg);