SUID root

["Richard B. Johnson" <root@chaos.analogic.com>]

It appears as though SUID root programs don't work on
linux 2.4.20, 2.4.21, or 2.4.22-pre6, or at least what
used to work no longer does.

One program tries to execute iopl(3). In the event that
it fails, it tries to set UID/GID to root after saving
the previous, then tries again.

The program exists in /usr/bin, properly owned by root. It
is set SUID, 4755, and otherwise works. Anybody have any
clues? Do SUID programs have to be re-written to use some
other mechanism? I need to have a user-mode program get
access to an otherwise unused printer port. It's a shame
to write a module just for this.


brk(0x804f000)                          = 0x804f000
brk(0x8051000)                          = 0x8051000
brk(0x8053000)                          = 0x8053000
time(NULL)                              = 1058364273
iopl(0x3)                               = -1 EPERM (Operation not permitted)
getuid()                                = 100
getgid()                                = 100
setuid(0)                               = -1 EPERM (Operation not permitted)
setgid(0)                               = -1 EPERM (Operation not permitted)
iopl(0x3)                               = -1 EPERM (Operation not permitted)
_exit(0)                                = ?
$ ls -la /usr/bin/debug
-rwsr-xr-x   1 root     root         6126 Jul 16 09:59 /usr/bin/debug
$ exit
exit

Script done on Wed Jul 16 10:05:02 2003


Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
            Note 96.3% of all statistics are fiction.