Busybox su leaves EUID unchanged

[Laurent Bercot]

># su userx
># id
>uid=203(userx) gid=203(userx) euid=0(root)
>
>Is this expected behaviour? From source I can see it does setuid() 
>which should also modify euid. If not then what could be the issue?

  As is often the case, the best debug tool here is strace :)
  What does "strace su userx id" say?

--
  Laurent