su/kdesu not working

[Dj YB]

On Monday November 9 2009 17:37:51 Chris Adams wrote:
> Once upon a time, Roberto Ragusa <mail at robertoragusa.it> said:
> > Chris Adams wrote:
> > > Once upon a time, Roberto Ragusa <mail at robertoragusa.it> said:
> > >> Big hammer:
> > >>   strace -f su -
> > >
> > > You can't strace a setuid executable.
> >
> > You are right.
> > Actually the execution will still happen, but with no root
> > authority, so it will not be useful for debugging.
> > Seeing some output incorrectly made me think it was working.
> 
> And to follow up to my brief response, you _can_ strace a setuid
> executable with an extra step.  If you run strace as root, you can pass
> the "-u <username>" argument, and it will switch users first (but still
> trace correctly).  So, as root, you could do:
> 
> # strace -u foo -f su -
> 

wow that was incredibly long output

the important line was about 1023 times repeating

[pid 24172] close(3) = 0
[pid 24172] close(4) = 0
[pid 24172] close(5) = -1 (EBADF) bad file descriptor
[pid 24172] close(6) = -1 (EBADF) bad file descriptor
[pid 24172] close(7) = -1 (EBADF) bad file descriptor
[pid 24172] close(8) = -1 (EBADF) bad file descriptor
...
[pid 24172] close(1023) = -1 (EBADF) bad file descriptor

that was before and after the password entering step.
any idea what to do next?
it seems like a filesystem problem