Date: Sat, 11 Sep 1999 14:12:00 +0200 (CEST) From: Blaz Zupan <blaz@gold.amis.net> To: freebsd-current@freebsd.org Subject: ps doesn't need privileges? Message-ID: <Pine.BSF.4.10.9909111406170.17275-100000@gold.amis.net>
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Please don't flame me if I'm asking something stupid, but I'm a bit
confused. I always thought that /bin/ps needs to be setgid kmem to be able
to display the process list. And this in fact seems to be the fact under
2.2.8:
/home/blaz> uname -a
FreeBSD server.amis.net 2.2.8-RELEASE FreeBSD 2.2.8-RELEASE #0: Mon Dec 14
19:22:23 CET 1998 blaz@server.amis.net:/usr/src/sys/compile/SERVER
i386 /home/blaz> ls -la /bin/ps
-r-xr-sr-x 1 bin kmem 176128 Oct 26 1998 /bin/ps
/home/blaz> cp /bin/ps /tmp
/home/blaz> ls -la /tmp/ps
-r-xr-xr-x 1 blaz bin 176128 Sep 11 14:08 /tmp/ps
/home/blaz> /tmp/ps ax
ps: /dev/mem: Permission denied
As expected, a copy of ps without setgid kmem can't display the process
list. But under 3.2 and higher, it is! Here is what happens under
4.0-CURRENT (same thing under 3.2):
/home/blaz> uname -a
FreeBSD gold.amis.net 4.0-CURRENT FreeBSD 4.0-CURRENT #0: Sat Sep 4
19:03:23 CEST 1999
blaz@gold.amis.net:/home/blaz/FreeBSD/src/sys/compile/GOLD i386
/home/blaz> ls -la /bin/ps
-r-xr-sr-x 1 root kmem 197820 Aug 7 12:42 /bin/ps*
/home/blaz> cp /bin/ps /tmp
/home/blaz> ls -la /tmp/ps
-r-xr-xr-x 1 blaz wheel 197820 Sep 11 14:09 /tmp/ps*
/home/blaz> /tmp/ps ax
PID TT STAT TIME COMMAND
0 ?? DLs 0:00.00 (swapper)
1 ?? ILs 0:00.00 (init)
2 ?? DL 0:00.00 (pagedaemon)
3 ?? DL 0:00.00 (vmdaemon)
4 ?? DL 0:00.00 (bufdaemon)
.....etc.
What am I missing? How is a totally unprivileged process able to display a
list of processes?
Blaz Zupan, blaz@amis.net, http://www.herbie.amis.net
Medinet d.o.o., Linhartova 21, 2000 Maribor, Slovenia
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