I was experimenting a bit and noticed something strange: setting the setuid bit on a copy of bash located at
/usr/bin/bash-test seemed to have no effect. When I ran an instance of
bash-test, my home directory was not set to
/root and when I ran the
whoami command from
bash-test, my username was not reported as being
root, suggesting that
bash-test was not running as root. However, if I set the setuid bit on
whoami, I was reported as being root in any shell, as expected.
I tried setting the setuid bit on
/usr/bin/bash as well and observed the same behavior.
Why is bash not running as root when I set the setuid bit on it? Could selinux have something to do with this?