Permission problems - though all three UIDs are 0

[Christoph Pleger]

Hello,

I want to ask for the possible reasons why a program, called from 
another program with setuid-root file permissions and an additional 
setreuid(0,0) to also set the real uid to 0, still gets an "Operation   
not permitted" error.

In my case, I execve lvcreate from the setuid-root binary. This works 
well when I use my program as a non-root user from the command line, but 
I want to call it is a non-root user from pam_exec PAM module and with 
that lvcreate fails.

Regards
  Christoph

PS: Please, no discussion about possible security holes in 
setuid-programs here