Exercise 9-5

[bumzy]

Hello, your ideas have impressed and helped me a lot. Thanks!
Exercise 9-5 answer may have a mistake.

// setuid()
/* suspend not possible */
/* resume not possible */
setuid(getuid());  /* Permanently drop privileges*/

[SteveLauC]

Indeed, for a set-UID-root program, setuid(uid) with a nonzero uid can permanently drop privilege as this will set RUID/EUID/SUID all to uid