SUID root

From: Richard B. Johnson (
Date: Wed Jul 16 2003 - 09:19:14 EST

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

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

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

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